1. You're using the old gimmicky page turn animations. I've never been a fan of these, and I don't think I'm alone. It would be much better to simply flip to the next page if I click the right side, or flip to the previous page if I click the left side. Optionally, you could add arrows, or setup the clicks for bottom right and bottom left corners.
2. I can click the edge of the page to go ahead one. I can't go to the previous page, unless I drag the page across.
3. Page turn animations got stuck once in a while, and the animation would be following my mouse, when it wasn't clicked. Then if I did click, I'd have two page turn animations moving at once.
4. It looks like a traditional book, forced into my widescreen monitor. If it's zoomed in, the bottom half of the book is cut off, so I need to scroll up and down constantly. If it's zoomed out, the book is a little box in the center of my screen.
5. I have no idea how many pages are in a book, or the percentage I'm done reading. Is this 10 pages, or 500 pages? That's kind of an important question.
6. The cover images on the homepage are pretty catchy, and I clicked on a few books because the art style or title caught my eye. A suggestion would be something like, http://i.imgur.com/YxdZgW3.jpg, where you have categories in a left column, search on top, and book covers on the right.
7. Center the page you're reading. For example, take a look at http://www.20thingsilearned.com/en-US. It suffers from the same page turning issues, but the book is centered when reading, and the left side simply fades off the screen. It also gives you a few thumbnails at the bottom and a table of contents, which is a nice extra.
8. Why not display multiple pages at once? Why leave the back of every page blank? Currently when I open your first featured book, I see http://i.imgur.com/BeaNf3B.jpg. Why don't I see something like, http://i.imgur.com/0YolAY3.jpg, where I get two pages at once to take better advantage of my widescreen? Or, you could even go three pages wide, http://i.imgur.com/lUs2aYl.jpg. I also added a simple arrow to click on the right.
In short, although I like the concept of creating and reading books online, the user experience is a little poor. I would never use the site to read a book in its current state. Nonetheless, I think there is some potential, but you really need to focus on the user experience for reading books.