I sent a dozen or so free copies of my first book to newspapers in Thailand. The book was set there so it seemed like a sensible move to get some coverage. Result - two reviews.
I did the same for my second book. Result - one review.
Vortex, my third book, came out last month. Again I got only one review - but this was it:
It made it all worthwhile.
If you're an author and you're wondering what the payback is - click the link. It's better than a fat royalty check - well almost.