On the legit front, they say that everytime a book is downloaded a % is paid to the publisher. I don't know how to verify that, and I have assumed they would have been shut down by now if they weren't legit. But I can totally understand people having reservations. That's why I looked for their explanation, didn't want to be downloading anything illegally!
I purchased a lifetime membership on the thought that as long as I download 12 books, I've got my money worth if they do go belly up (assuming most ebooks sell for $10ish).
The site is definitely set out badly and hard to navigate. If your a member having trouble, make sure your logged in and you should see a forum halfway down, I think called ebooks (sorry on my phone so this is from memory). That's where you download from. Hope that helps.
Definitely not a site for everyone, it's annoying, frustrating and time consuming. But for the price I've been happy with it.