A unique feature of Goodreads is that there are giveaways. Famous authors and virtually unknown authors (like me) alike offer copies of their new books in giveaways. You can register to win the giveaways and the only thing you have to do if you win a giveaway is read the book and write a review of it on Goodreads. Of course, they can't make you do it, but if you don't write a review, you probably won't win a book again.
I've joined the bandwagon and offered
How exciting to think that 500 people I would otherwise have had no access to have read what my book is about!