Finding good quality crossdresser story ebooks can be a whole journey. The mainstream stores like Amazon have a decent selection if you use the right keywords—think 'crossdressing romance' or 'gender disguise' instead of just 'crossdresser'. 'His Secret' by Adriana Herrera is a solid contemporary M/M romance with that element, and the Kindle Unlimited catalog is surprisingly deep if you're patient. A lot of older historical romances, like some Mary Balogh titles, play with the trope too, where a heroine has to pose as a boy for safety. The trick is wading through the stuff that's just fetish fuel without any character depth. I've found the reviews on Goodreads specific to the 'crossdressing' shelf more helpful than the store algorithms, honestly, because readers there will flat-out tell you if the portrayal is respectful or just a cheap plot device.
For more niche, character-driven stuff, I've had better luck on Smashwords. The search filters let you get granular with tags, and a lot of indie authors publishing there are writing from a place of genuine exploration of gender presentation, not just for a quick titillating scene. The quality varies wildly, but the preview function is a lifesaver. Also, don't sleep on serial platforms like Scribble Hub. Some of the best slow-burn fantasy stories with crossdressing protagonists I've read started there, often updating chapter by chapter. You get to see the author develop the concept over time, which beats a rushed novella any day. My last find there was a 200-chapter epic about a knight hiding her identity; it had the political intrigue and emotional tension I craved, and it was free until the author compiled it into ebooks.