Every Friday I take the initiative to search through thew newly free titles on Amazon, and to identify those that might be of interest to trans* readers, fans, and lovers. Even if you don't have a Kindle, you can still download the titles through one of Amazon's free reading applications, and covert it (if need be) with Calibre. I can tell you I do most of my reading on my iPad, using Kindle for iPad, and it works beautifully.
Please do be sure to check the price before downloading anything, though, as most freebies are limited time offers, and some are specific to certain regions.
Sissy Princess Sperm Whore: a tale of BBC Creampie addiction
Alien Gender Swap Experiments Bundle
Lucky Slots Gender Swap (Bimbofication Body Switch Tales Book 1)
The Challenge: Femdom, Forced Feminization, Caning and Chastity: A BDSM Fetish story, of Female Domination, Forced Feminization & Enforced Male Chastity (The Teacher's Pet Femdom & BDSM saga Book 1)
Feminized by the Pop Star: Part 1
Just A Taste (Boy Wife Book 0)
Sentenced to Gender Swap: Male Maid
Hugh Looks Like a Lady: Gender Swapping the Frat
Punished By Mrs. Claus (Naughty Christmas Erotica)