No manga request this time. A while back someone made a post about gender bender light novels when someone recommended the Safehold series (not a light novel). Got me thinking about what else there was in literature. The Safehold series, female robot modifies herself into a male one, only touched upon it in the first book then its mostly forgotten. And the Tamir triad, hair to the throne transformed into her dead brother and grew up not knowing shes female, are the only once i can think of. Looking for other sci fi and fantasy books in the same vein.

"The oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown"

These Old Shades by Georgette Heyer - The female lead has passed as a boy for many years and spends a good chunk of the novel as a page (young male servant). Not fantasy/SF, but Heyer is one of my favorite authors and I generally only read fantasy/SF...

The Marvelous Land of Oz, which was the sequel to The Wonderful Wizard of Oz, also features a princess hidden as a boy by magic. It may even have been an inspiration for the series you mentioned.

In MM Romance:
Rebeca Cohen, The Actor and the Earl, haven't read it so I can't tell if it's any good.
Catt Ford, The Last Concubine, haven't read it either, doesn't seem like my kind of book, but I came across it while searching, so here it is.
Marie Sexton, Cinder, an MM version of Cinderella, kind of cute.
Lissa Kasey, Hidden Gem, I tried to read this one but I didn't like it and dropped it, it's kind of graphic in some moments, but it kind of fits your request, so yeah.

Non MM:
Lynn Flewelling, The Bone Doll's Twin, read it a long time ago and don't remember it much, but I remember I liked it.
Max Gladstone, Full Fathom Five, very good, it's part 3 of a trilogy though, I recommend reading the previous 2 parts first
I don't quite remember, but I think The Weavers of Saramyr could have had some elements like this, but I'm not sure. You may like the book because it kind of reads like manga, there's a lot of references to Japanese culture, but unfortunately the plot is a bit... meh.
And lastly, here are two random YA novels I came across while browsing goodreads, haven't read them but who knows, maybe they will fit: Defy and The Sentinel Mage

EDIT: I just noticed you mentioned the Tamir Triad in your post, but I'll leave it here

invisible monsters by palahniuk yeah not sci fi or fantasy
left hand of darkness by le guin should kinda fit

Quote from Hanae

MM Romance

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"The oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown"

[quote=Hanae]In MM Romance:
/quote]

Quote from EternalNightmare

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Yaoi. BL. MalexMale.

I didn't want to write yaoi because this term is mostly associated with manga and goodreads categorizes such books like this

@Hanae: The OP is a guy, you know. It's best not to recommend guys M/M unless they specifically ask for it, imo. (Hell, I'd say the same is true for girls) Waste of his time and yours.

But there are other people here who could be interested, so I just listed everything I knew and specified which books were M/M and which weren't, so that the OP or anyone else could ignore them if they weren't interested.

If no one have anything more to come with, anyone got a suggestion for where i could continue my search?

"The oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown"