I read tons of free books on my kindle. I even pay for one occasionally. Except for the self-published ones, almost all the free ones are very old, and usually quite good, but I’ve many happy hours reading them.
I only do download the ones with good reviews. I don't want to waste my time with obvious crap. But you can pay a lot of money for a book and still not enjoy it. I have a folder called "bought" for books I actually spent money on (it's a small). Just started one this day, read only the first chapter but like it so far (lol)...
Night of The Crabs (Crabs Series Book 1) [$4.88 - it's cheaper in euros]