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.
Million Dollar Femboy 3: Spoiled Rotten (Gay crossdressing public sex erotica)
The Trophy Wife #3: Feminization of the Cuckold Husband
Miss Futanari Feminizes and Humiliates Her Cuckold (Sarah and Miss Futanari)
Femdom : The Game : Female Domination, BDSM, Forced Feminization, Bondage & Forced Bi
Gender Swap Pawn Shop 1: Plenty of Panties (Gender Transformation Feminization Erotica)
Chance Encounter with a Transvestite: Sucking My Futanari Mistress' Cock