I am the author of over a dozen photography books and have recently produced my own eBooks, which are now available on Kindle, Apple iBook and general eBook formats. These include -
Practical Digital Landscape Photography (NEW! Listed on Amazon, Kobo and Nook bookstores)
Practical Digital Portraits
Get Started in Digital Glamour Photography
Digital Photography Essentials
All available for Kindle, iBook and other eBook formats. Find them on Amazon, the Apple iBooks store and at Smashwords (www.smashwords.com).
There is a new 2nd Edition of Get Started in Digital Glamour Photography, specifically designed for the iPad, featuring hi-res photos, interactive elements and audio, only available from the Apple iBook store.