Apps for accessing audio and e-books

I am interested in using apps that can provide book content in audio book and E-book formats that I can use on my I Phone 4s and I Pad 2.  Unfortunately, the rnib are well behind and only provide computer access for their DAISY library content and there are not many academic books in the library that I can use in my PhD.  I have seen the Book Share and Kindle AP's but don't want to download them until I can get some more information about them:

1.  I already have the PC version of Kindle but its not that accessible using JAWS 13 and I am annoyed by the preset USA voices and the fact that I can't navigate within the available academic books to find references and quotations (my American friends don't annoy me, only the fact that I can't choose JAWS to read the content.  Is the AP store AP the same or can I use the supplied UK voices and navigate within the content?

2.  The Book Share app looks to be very accessible but I understand I have to join Book Share to get all the content from the UK.  Does the AP do what I want i.e. enable me to navigate within the content or do I have to read everything?  I'm happy to purchase a membership to Book Share but I'm not sure that I will get access to all content (copyright rules).

Also, if anyone has any recommendations for AP's that will help me with listening and navigating audio books or E-books, that would be useful.  I am particularly interested in navigating like I can do in the Milestone 312 for DAISY audio but also something that provides better navigation than the Milestone 312 does for E-books.

Regards,

Steve.