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.
Gender Swap Pawn Shop: Transgender Erotica
Mind Swap: Day 1
Bitcoin Bimbo: Science-Fiction Transgender Erotica
Gender Bender Forever: Erotic Fiction Bundle
Seeking the She-Wolf (Shifter Gender Swap) (Anything for the Alpha Book 1)
The Price of Changing (Transformation, Futa on Female, Futa on Male)
Transformed by the Futa Mad Scientist (Futa Adventures)