These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Young Wizards
Badass Decay: Justifed Trope. Dairine starts off with a greater amount of power than her sister when she becomes a wizard n the third book and then falls to just above normal in the fifth. This fall is normal and expected; every wizard starts off with greater power for their initial ordeal. By the time the power drops off, their skill and knowledge increases.
and/or Nita's younger sister Dairine. She gets less Sueish after she has to deal with no longer having enough power to do anything she wants and not knowing enough to make up for that, especially since that happens when her mother is dying of cancer.
Unfortunate Implications: Darryl's autism is portrayed . . . less than sensitively. To put it in perspective, Kit's mom's reaction to hearing he's autistic is basically "oh, that's awful". The whole book treats it like a big tragedy and if that wasn't bad enough he cures himself of his autism by splitting his autistic self away and leaving it behind in the universe he created with the Lone Power. Yeah, it's pretty bad, but you have to give Duane credit. She not only recognized readers' criticisms regarding this issue but fixed them in the new New Millennium Edition of the book.
Word of Gay: Tom and Carl. According to a troper on this site, he "was an acquaintance of Diane Duane's before she moved to Ireland, and was present when she confirmed to a small audience at a reading that Carl and Tom are indeed a gay couple — but added at the same time that she'd never say so explicitly in the books" (partly because they're books in the Young Adult section, partly because they're based off two straight friends of Duane's). Frankly, you could call them Heterosexual Life-Partners and no one would be the wiser if all they read are the books.