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.
MIstress Tasha's Rainbow Girls 1, Carl Becomes Carla (feminization)
fuTA Complete (Futa on Female Transformation Erotica)
Double Delights (Futa Subway Express 1)(futa-on-female, menage, cuckolding, public fun erotica)
Hawaiian Treat (Futa on the Beach 1) (Futa-on-Female, Cuckolding, Menage, Hot Wife Erotica)
SISSY MAID in the mirror (a sissy maid missy sister series Book 2)
Claimed as the Futa's Mate (Futa in the Forest 1)(Futa-on-Female, Paranormal, Outdoors, First Time Erotica)
Sex Change - Male to Female: An Essential Guide for Understanding the Process of Gender Reassignment Surgery and Getting to Know the New You
301 (Just Let Go)