The site looks neat! Clean, easy on the eyes, love it!
But (aren't there always?) a few points:
What format are those books? I can't find anything about it. emellaich already said it, are those books DRM'd or not? (emellaich: at fictionwise, it's very clear what format the books are, what is allowed (such as reading aloud, printing, etc) and whether there is DRM on it or not).
One thing I don't like at Fictionwise, which you also have on your site: the categories are too few. Let's say I am browsing your site for a book, no matter what book (as in, I don't know an author, nor a title, I only know I want a sci-fi book), I have to browse 123 pages before I've seen all books. What I"d love to have is something where you can narrow your choices down. Look at Audible.com (select Sci-Fi and Fantasy, select view all titles, you can then narrow your choices down)
I'd love to see the implementation of the wishlist and bookshelf. Is it okay to create a dummy account?
I like the option to search for a series! But it didn't work as it should (I think). First, I went in search of a series and found one in the Fantasy category: "the Chronicles of the Necromancer" There should be at least three books, by Gail Z. Martin. I then went to the Advanced Search and searched for the keyword "necromancer" in the "Book series" field. I had the combobox on top filled with "Any" (I presume that means any word should be in that field, it needs a label, I think). I got 14254 books as result... I think it's not working at all
One thing should really be looked at, and that is the mouse cursor. griffonwing already mentioned it as well. It looks like the anchor isn't exactly spaced over the text and this will become highly annoying very soon.
Conclusion: it's looking very promising, if those last few points can be cleared up (and if that narrowing down of choices can be implemented, it'll be awesome!)