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.
Steamy Gender Bender Scenes: Transgender Erotica Bundle
TRANSGENDER EROTICA: Sissy Swaps: Gender Bender Erotica Bundle (Male to Female Gender Switch Transformations Book 1)
Feminised: Erotic Gender Swap Boxed Set
Taken by the Futa Firefighters (Taken by the Futas 1)(Futa-on-Female, BBW, Menage, Cuckolding, Interracial Erotica)
Femdom : The Game : Female Domination, BDSM, Forced Feminization, Bondage & Forced Bi
EROTICA:THREESOME (Feminization FFM Fiction Sex Stories): XXX ... Dirty Box Set Collection Series 2 3 1)
Born Wrong?: A Transgender Teen's Journey
Five Things You'll Face as a Pre-Op, Pre-T FTM
The Sex Changing Princess Bride (Wishing Wheel Septet Book 1)