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.
Femdom - Grant Gets Feminized In Diapers ((ABDL, Sissy, Feminization) Book 1)
Nanny's Futanari Surprise (Futa on Female Transformation)
Fifty Shades Pinker (The Ultimate Sissy)
Cuckold by the Futa (Futa Marriage Counselor 1)(futa-on-female, cuckold erotica)
Sissy for My Step
The Operation (Gender Bender, Feminization)
Out Of This World (Alien transformation erotica): The One Where Zach Gets Probed
Dorm Submission (Dominated at St. Futa College 1)(Futa-on-Female, BDSM, Menage, College Erotica)
Dress Code (St. Futa College 1)(futa-on-futa, futa-on-female, exhibitionism, nun, spanking erotica)
Dirty Little Secret: An Exhibitionist Gender Transformation Story