From the press release:
vBookZ is intuitive, easy to use, and offers to the iPad users a whole new reading experience. Acapela speech synthesis comes in to turn the written content into pleasant speech, without ever having to watch the screen.vBookz is NOT 'books on tape': it is a live text-to-speech generator with no need for conversion nor stored books files. It is a new way to enjoy reading: eyes-free reading while on the move, driving or just relaxing, assisted reading for the sight impaired or audio feedback for children or those learning to read in a foreign language.
vBookz adds to speech capability orientation and navigation tools that enhances the reading experience, combining two senses together - sight and hearing. An interactive cursor allows users to follow along, pause reading or even repeat lines or paragraphs to ensure reading comprehension.
I'm not terribly impressed. It costs $5, duplicates a feature of iBooks, and is limited to 30k public domain titles (I can't see a way for a user to add more).
On the other hand, Acapela specializes in TTS. Their apps are very, very, good.