I really like Goodreads. Although I also use Shelfari and LibraryThing, it is Goodreads where I interact most with books and readers.

I have done giveaways in the past. They seem like a good idea and are favoured by Goodreads staff because it means their users get freebies without it costing Goodreads a penny. I've found it has one large benefit for authors: it means people who haven't heard of your book become aware of it. More people mark it as "to read". There is a downside though. Every book has an ideal audience which is smaller than the full reading population (Karl's Law). Whether it's a Western or a young adult vampire romance, some readers will devour it, others will revile it. You want to target your book only at the former. Then everybody is happy. However, in a Goodreads giveaway any reader can tick that they'd like a copy. So you get people applying for every book just to get something for free. Then Goodreads software chooses who gets the books. This is where it goes wrong. My experience is that of all the books I've sent out for free via Goodreads giveaways, only a small percentage (possibly one in ten, but hard to know for sure since Goodreads doesn't share this data with authors) actually reviewed the book. This is a far lower percentage than if I'd chosen my own readers. It gets worse: I've seen reviews along the lines of "This book really isn't my kind of thing..." THEN WHY DID YOU SAY YOU WANTED A COPY? DON'T YOU READ THE SYNOPSIS? So the end result can leave you worse off. Goodreads also makes costly mistakes. Once I selected a giveaway just for the UK. I triple-checked the details as usual. Then Goodreads sent me a list of US readers to send the book to! It was incredibly expensive. The end result is that Goodreads giveaways can be a mixed bag for authors.

What else can you do? A targeted giveaway is much better. It's the logical approach. In August last year I made the mistake of being logical, even though I thought I was adopting best practice.

I was very selective. In this case a Goodreads review had likened my book to another, a positive comparison, suggesting readers would like both. So I looked up that book on Goodreads. Made a note of some of the people who absolutely loved it. Checked their profiles for anything that might suggest they wouldn't like my book, or that they didn't want authors to contact them. Then from my shortlist I sent a very polite message, telling them that a Goodreads review had likened my book to the one they loved and if they would like a print or e-book copy for free I'd be happy to send one (note that I didn't even ask for a review in exchange). If not then I apologised for contacting them, said they could just ignore my message and I'd never contact them again. It didn't seem to be against Goodreads rules, it was respectful, and it was as selective as it is possible to be.

The result? Overwhelming gratitude. Loads of messages saying how they'd love a copy, some of which can be found below.
"ok, that's awesome. ... It is not everyday that I get an e-mail from an author offering me his/her book."

"Hi Karl! I don't mind at all! I love talking to new people and the possibility of reading new books! I would love to read this book--it sounds really interesting!"

"Many thanks for contacting me. I would be happy to read and review a copy of your novel"

"Thank you very much for contacting me. I'm always excited when I have a chance to experience new books."

"Thanks for thinking of me and I certainly didn't mind you getting in touch."

"Thank you for your message! I just read the description of your book in Goodreads, and I'm hooked! I'd love to read it ... Anyways, thank you for getting in touch; it was a wonderful surprise since it is such a task to look for books to read and this time, a book reached me."

"Well, this certainly sounds interesting. I would like a copy, the print version please. And...could you possibly sign it for me?"

"Hi Karl, no I don't mind at all. I would love to read your book. ... Please get in contact if you would still like me to read a copy."

"Your book really does sound "right up my street". ... Thank you for the offer, I really look forward to reading your book"

"Thanks for the note! I would love a printed copy of your new book. It sounds interesting and I look forward to reading it! ... Thanks for contacting me - I truly can't wait to delve into it!"

"Thanks for the offer. I like your blog a lot (still getting through the Manchester research post in fact). ... Cheers!"

"Thank you for getting in touch and - NO - I don't mind at all. Your book sounds intriguing and I would definitely like to have a look at it. ... Looking forward to hearing back from you."

"Thanks for the message and congrats on your book. I actually used to live in Manchester for a few years (scarily close to Strangeways!) so this is of particular interest. I would like a copy ... Thanks again"

"Hi Karl, I love hearing from authors. ... I'd love to have, read and review a copy. ... Thank you for contacting me and I look forward to getting your book"

"That's very kind of you Karl, I've actually had your book on my Amazon wish list for a little while...it sounds great!! No need to e-mail a copy, I'll buy it tomorrow (cuz that's when I get paid;) lol...I appreciate the thought and look forward to reading your work."
I knew it would cost me a lot, since I didn't exclude people based on country, and as a result agreed to post copies to Canada, Australia, and the US. Lots of Goodreads users benefited, were grateful, loved the book. A win!

Not quite. One person complained to Goodreads (without contacting me). As a result my account was threatened and an email from "The Goodreads Team" told me that my message had been
"flagged as self-promotional in nature. Please note that it violated our Terms of Service to send such messages on Goodreads. Nearly all of our members consider unsolicited messages from authors to be spam [...] Refrain from such activity in the future."
Well, that was strange. I think everybody but one person was incredibly pleased with the offer and took me up on it (which Goodreads could confirm based on the messages I received). So although it is true that non-targeted communications are unpopular, and scattergun marketing benefits no one, I was so careful, selective and polite that 99% of the Goodreads users I contacted were really pleased. So why do they have to miss out in future because of one grumpy sod? Why do people who don't like something get given more of a voice than those that do? It's not something that Goodreads explains, or is publicly discussed. Since even one person can get you flagged, and it doesn't matter if the other 99% loved you getting in touch, it's a system in favour of the complainers and inaction. A skewed bias.

I did check the Goodreads terms, and tracked this down, which seems to be the only bit they could be referring to (I had to edit out various clauses to make something easier to read - hence missing it the first time):
"You agree not to engage in any of the following prohibited activities: [...]  (viii) using any information obtained from the Service in order to [...] contact [...] any Member without their prior explicit consent"
It left me rather disgruntled. Goodreads could easily have a more sensible system, where users can tick a box stating if they don't want authors to contact them, or conversely a box saying they do want offers of freebies from authors. Then everyone would be satisfied. Instead you can be banned for messaging someone responsibly, even though Goodreads allow you to contact people responsibly. The only safe option if you're an author is to never contact people.

The Goodreads Team did not reply to the email I sent them about this. Yet look again at the list of messages I got, above and below: Goodreads users lose out because of the current policy. I can't use this marketing technique again to target people who would really enjoy a free copy of my books. I've contacted Goodreads again and will include any response of substance. I still like Goodreads but it seems to be a case of a general rule applied by them even when it is counter-productive.

Here are some of the other messages I received, just to show that I'm not making this up!
"I'd love to read your book. ... Looking forward to reading it :)"

"Thanks for your message. Yes, I'm interested!"

"thank you for your email and I would love a copy of Cold Fusion 2000! Let me know how I can get a copy of your book."

"Would love to read :) Thanks and good luck!"

"Sounds very interesting. Send it my way I will read it!"

"I would love a copy. Thank you."

"Thanks for the getting in touch"

"Thanks, I look forward to reading it :)"

"Thanks so much for your email and yes, I would love to read your book"

"sure! I would love a copy, it sounds good :) thanks for thinking of me!"

"Hi Karl, that sound great. How do I go about downloading?"

"What a lovely email to receive on a Wednesday morning. Your novel sounds very interesting and I would live to read it. Thank you for the offer."

"Thank you very much for contacting me! I have had a look at the blurb for your book and it looks right up my street! I also loved geek girl and the Rosie project! I would love to read your book ... I look forward to hearing from you!"

"I would love a copy of your book - it sounds intriguing! Thanks for the opportunity to read your work."

"Sounds interesting and yes, of course I would love to! Thank you for sending me your book"

"Thanks so much for your kind offer of a copy of "Cold Fusion 2000". I'd love to read it, as it does sound interesting."

"I never turn down a free book, lol. Seriously, I would love to read it."

"You certainly have got me interested! I'd love to see a copy."

"Thank you for considering me for reading your book."

"I'd love to read your book and see if I can add it to my go-to recommendations list."

"Thanks for getting in touch!"

"Thanks for the offer. Your book sounds interesting and I'd love to give it a read. ... Thanks again for thinking of me!"

"That sounds great! I thought the rosie project was pretty awesome and I'm intrigued by the description of yours so I would love to read it!"

"Thank you for your message. There was no bother at all! I would be honoured to read and review your book."

"Would love to get a copy of your book. ... Thank you for contacting me."

"I would love your book thank you so much for considering me to do so."

"Thanks for your message. Yes, I'd very much like a copy of Cold Fusion 2000 please."

"Hi Karl. Sounds good. I'll read your book for sure. Thanks!"

"Thankyou for getting in touch with me, how nice. ... It sounds fabulous."

"Thank you for your offer of a free copy. I certainly will be taking you up on this offer."

"I am looking forward to what sounds like an enjoyable read. Thank you."

"Hi there! I would love to read Cold Fusion 2000 ... Thanks very much!"

"Yes thank you Karl would enjoy a print copy of your book"

"thanks for the message. I'd love to read it!"

"Thank you for contacting me. I would absolutely take you up on the offer ! Sounds like something I'd enjoy ! ... Thanks again !"

"Thanks for the email. I would be happy to red and review your book for you."

"I'd aboslutely love to read your book. ... Thanks a lot for giving me the chance and I'll spread the word as soon as I finish reading it."

"I would never say no to a free book!"

"I would be delighted to receive a FREE copy of your book - it sounds like something I would enjoy ... Many thanks"

"Thank you for contacting me, I'd be delighted to read your book. I took a spin through the synopsis on your site and it sounds fascinating and I would very much enjoy the opportunity to read your book ... Thank you again for getting in touch, it was a welcome surprise."

"Your book sounds really fun and I would love to read it!"
KD update: I got a response from Goodreads (2014-04-04):
Hi Karl,
Thank you for reaching out to us.  We can certainly understand your frustration, as it sounds like several members responded positively to your offer.  While thoughtful, targeted promotions can be extremely helpful in launching a new title, we do consider messaging large numbers of members of the site to be spam, per our author guidelines.
For every member of the site who responds positively to such offers, we have found that there are many others who report them as spam.  In addition, if we allowed this, our top reviewers could end up receiving dozens of these messages a day.     We appreciate your feedback, and your suggestion for an opt-in to messages from authors is interesting.  We'll certainly take it into consideration as we look to improve our author program.  In the meantime, as one way to reach a specific audience of readers, we encourage authors to take advantage of our author blogs or self-serve advertising options. For example, with our ads, you can target your advertising by genre. There are also several groups on the site that allow authors to post offers of books for review.  
If you have any further questions or concerns, please feel free to email us.
Sincerely,The Goodreads Team