I am not going to slam any sites but put a warning out there. Many of these "free" ebook sites are giving you illegal, pirated ebooks. The authors are not getting their royalties. This may not sound like a big deal but if one person buys a paper book, they can share it with only one person at a time. The royalties lost are only a few dollars. If someone posts an ebook on one of these pirate sites, thousands can download this book costing the author hundreds in royalties. This is how they make their living. This is how they can afford to write the stories we enjoy. Downloading a pirated ebook is just plan stealing.....accepting stolen goods.
Most authors try to get their books removed from these "free" sites. It's very difficult as many are based in foreign countries. As tempting as it is to read your favorite author's newest release free, unless their publisher or a authorized, recognized why cheat the author.
I'll get off my soapbox now.