Percy Jackson is written as having ADHD, because the writer's son had it. I liked it, but maybe the "it's actually a super power" thing might rub some people the wrong way.

A lot of Neal Stephenson, but especially Cryptonomicon, The Baroque series, and Anathem... though with the last it's not so much the narrator as a lot of other main characters.

"Time to Orbit: Unknown" by Derin Eldala is great. Its definetly written in an ADHD style

https://derinstories.com/2022/06/04/001-the-problem-with-the-javelin-program/

Its an ongoing web serial. Be careful, apparently it made a surgeon miss surgery twice

While I don't think that a main character has ADHD specifically, The Stormlight Archive by Brandon Sanderson deals with various mental health problems. I will say that Stormlight is on a whole different scale though. Looks like the first book is about the length of the whole murderbot series and there are 4 books out currently with another coming in December

This might not exactly be the sort of thing you're looking for, but I recently read and loved Blindsight

Not ADHD, but definitely neurospicy. The main character has half a functioning brain, with many technological augments, and is pretty far from NT as a result.

Anyway, I highly recommend it. Super interesting book. It's about alien first contact, although not in the way you might expect...

A Closed And Common Orbit - the main character, Lovelace, is not explicitly neurodivergent (she's an AI), but there are so many parallels with the experiences of neurodivergent people it's worth a mention. Probably more relevant to autism than ADHD. And, unrelated, lots of parallels to trans experiences if that's interesting to you.

Not a book, but one of the Daniels has said that Everything, Everywhere, All At Once is based on his experience of having all 80 of the HDs.

Also, having written that like that reminded me that there’s a character in the Dogman kids graphic novel called 80hd

[off topic?] "X X" by Rian Hughes features an autistic hero. Because of the creative way the author uses graphics, it's a book that loses a lot if you get the audio version

I can't be convinced that the main character of Lucky Wander Boy isn't autistic, considering the obsessions he has and the ritual he performs at one point.

Great, but very weird book about a writer who likes retro video games trying to find an arcade machine of his youth that may even have mystical powers.