"River God" by Wilbur Smith is a good book, and has been mentioned here before. Our hero is a mid-teen at the time of his nullification, however, and then grows up within a couple of chapters. If you like 'things Egyptian', with or without the eunuch topic, it's still a good read.
"Cry to Heaven" by Anne Rice, while a huge departure from her normal fare, is just OK. It's not blah, but it stretches things a bit. No pun intended. It's all about a revenge plot in the height of the Italian castrati era, and has a nice twist at the end. The sex-capades are a bit on the side of pushing it, though, and our hero (while castrated a bit older than most) is the main focus of the novel. It's not a laugh riot, and there are points where you struggle to get through it. As I recall, fans of Rice's vampire Lestat, etc., were shocked by this book, and rightly so. It's probably one of the more famous ones out there with eunuch characters, in that she built the whole story around a young boy being castrated and wanting revenge.
"Eunuch" by Lustgarten, as I said, was just awful. My compassion for the hero ran out shortly after he escaped into the real world, and when the cloning thing came up, I was done. I forced myself through it, though. You can read it up to that point, but then it goes over a cliff. I have to give him a "E" for effort, instead of just a flat out "F" for fail, in that he managed to get it published to begin with!
"The Persian Boy" was entertaining, and quite historically accurate. You feel for Bagoas, the hero. There's one scene early on when Darius is overthrown (?) - well, someone is overthrown, I think it was him... and the Bagoas is hiding, on the run, realizing that he's "loot". Mary Renault does a great job building his character, leading up to, during, and the period of adjustment after his castration/nullification and how it affects him mentally. If Lustgarten had read this one first, or paid attention to it if he did, then "Eunuch" might have been a better read. You genuinely feel for Bagoas, and wonder where the story is taking him next.
I don't know if there is a novelization of the film "Farinelli", and frankly, I hope not. It couldn't be much worse than the historically inaccurate movie, though. About 10% of the film's run time is spent on Carlo's (his real name) childhood, and the whole plot of Farinelli vs. Handel is overblown.
"Let the Right One In" or "Let me In" has seen a couple of movie adaptations, and while the whole idea of our hero being a eunuch is just a throw-away shock bit, it's there. If you're into low budget vampires, I suppose you might like it.
"John the Eunuch" is a series of mystery novels by a group of authors. John, however, is an adult when castrated as a result of being captured in a military campaign by the enemy. It's sort of like "Murder She Wrote", only with a Byzantine Era adult eunuch instead of Angela Lansbury. They're not bad novels, if you're into that sort thing. Younger eunuchs are only mentioned rarely in passing, though. You can find them here: CLICK HERE
(
https://www.thriftbooks.com/series/john ... earch%20Ad% 20Test&utm_term=thriftbooks&utm_content=heYWuUrg|dc|pcrid|77240706869719|pkw|t hriftbooks|pmt|bb|product||slid||pgrid|12358510981 99146|ptaid|dat-77240712317549:loc-190|&msclkid=2fb61f9a2c87137ebd0b40b092222d25)While society in general has certainly opened up much more than it was when some of these books were published, you're still not apt to find very many works with a young eunuch as a protagonist. Even George RR Martin's much-hyped "Game of Thrones" didn't really center on younger eunuchs, but for a little bit in his description of the making of the Unsullied. To be honest, I didn't read any of it, or watch the series. I was told by someone that had he submitted the chapter about the Unsullied to EA, that I would have rejected it on the grounds of cruelty for the sake of cruelty only. It's probably a foregone conclusion that there's not a market out there for (shameless self-promotion here!) a hardback or even paperback run of "The Boys of Blue Creek." Just not going to happen. Perhaps the collected works of Byzwriter here on EA could be? Look him up if you haven't. He's one of the greats at EA.
We've come quite a ways in the last 20 years or so, but mainstream just isn't ready (and maybe never will be) for a such a topic.