Menu sliding back
It happens to me, too on my Nexus 7. I like seeing the bookcovers on the virtual shelf, and my other apps, Kindle, Nook, Moon+ and Mantano don't have any problem with doing that.
I mainly use Moon+ these days. I can use the Favorites shelf to create categories for my books, and the app is nice and responsive, with all the fonts I'd ever want. It also sorts out weirdly formatted books for me. I used to use Cool Reader a lot, but the scrolling thing pushed me away.