Reddit reviews The Hero and the Crown

The Hero and the Crown by Robin McKinley

The Earthsea series by Ursula LeGuin

The Dragonlance Chronicles by Margaret Weiss and Tracy Hickman

The Belgariad and The Mallorean by David Eddings

The War of the Blades series by J.D. Hallowell

The Shannara series by Terry Brooks

I really loved the Wise Child trilogy, The Hero and the Crown/The Blue Sword, and the Sally Lockhart series (and all of Phillip Pullman's books) as a kid.

I've read and loved almost all of the recommendations already here (TAMORA PIERCE). But to add some that haven't been mentioned (and trying really hard to not overload you with 20 books at once), I read and reread Robin McKinley's The Hero and the Crown and its prequel so. many. TIMES. Maybe even more than I reread Tamora Pierce. Patricia McKillip, Maria Snyder, Patricia C. Wrede (Dealing with Dragons quartet), Althea Kontis, Francesca Lia Block, Libba Bray and Susan Fletcher (Dragon Chronicles) are similar authors to check out for awesome female-driven fantasy, with varying degrees of lightheartedness. Wrede, Fletcher, Snyder and Kontis all wrote books that lean a little less epic/serious, Block writes a lot in prose that's also a very quick (but more intense) read, McKillip tends to be more wordy but beautifully so, and Bray can kind of go either way depending on the series.

For more contemporary fiction, RACHEL COHN (of "Nick & Norah's Infinite Playlist"). Her Gingerbread series has content a good deal more mature than Angus, Thongs, etc., but her style is similarly irreverent and witty and really fun. Seriously, check her out. Sharon Creech's Walk Two Moons is like a much younger version of Cohn, still zingy and sweet. For a quieter modern-day read, Garret Freymann-Weyr writes realistic (more mature) young adult relationships, and introduced me to the idea of bisexuality in a sort of roundabout way.

Julia Alvarez relates stories about the Latina-American experience incredibly well, although I think the first book I read by her takes place solely in the Dominican Republic. According to my reading list, I guess young me got sick of reading about other white people, so I'll add Marjane Satrapi's hilarious graphic novel Persepolis and the more sedate Shabanu series by Suzanne Fisher Staples.

I'd also strongly second comments for Gail Carson Levine, E.L. Konigsberg, and did I mention Tamora Pierce?

(I tried to link a lot of authors to my faves from their work, but I won't be mad if you never look at any of them. Is your reading list long enough now? Also, I know you didn't ask for a ton of fantasy/historical fiction recs, but I think a lot of us defined our teenagerhood by and identified more strongly with one of those series or another.)

tl;dr my top three recs that haven't been mentioned yet are Rachel Cohn, Julia Alvarez, and that one duo by Robin McKinley.

Reminds me of the spiral stairs in The Hero and the Crown.

I'd recommend The Blue Sword and The Hero and The Crown by Robin McKinley. I think I read them first in Grade 2 or 3, and I still love them and reread them often. The Blue Sword is about an orphan girl who is kidnapped by a desert king and trained as a warrior to save his nation, and The Hero and The Crown is a prequel about an ancient hero who fought dragons.

She writes a lot of other books that might be acceptable, often retellings of fairy tales. However, absolutely do not let him read Deerskin at this age. It has very disturbing themes, even for adults.