I recommend the original DragonLance trilogy: Dragons of Autumn Twilight, Dragons of Winter Night, and Dragons of Spring Dawning all by Margaret Weiss and Tracy Hickman. If he likes them, he might want to check out more of the series--in particular, I recommend the Twins Trilogy, as well as Dragons of Summer Flame, The Soulforge, and Brothers in Arms.
Mairelon the Magician by Patricia C. Wrede is a fun read. It's very alternate history; the society is loosely based on Regency/Victorian era England, with just a dash of sorcery thrown in. There's a sequel called The Magician's Ward, but I haven't been able to get my hands on it and thus can't truthfully rec that one. D=
A Great and Terrible Beauty by Libba Bray is another alter-historic fantasy novel. It's a rather...female-oriented novel, as it's told almost entirely from the viewpoint of a teenaged girl in Victorian era England, but if he's into Harry Potter then the school setting coupled with the main characters coming to terms with their budding power (the school itself is not a magic school, but the girls all manage to learn a thing or two about witchcraft while they're there, anyway) might perk his interest. It's a very well-written and enjoyable book, and I've gotten a few of my guy buds to read it and they seem to enjoy it.
Wicked by Gregory Maguire is awesome. The magic and fantasy setting are secondary to the big question on the nature of evil, but they provide an interesting context for the story/morality play and it's a new and exciting viewpoint on the world of Oz. There's some sexuality involved, but not a whole lot of it; definitely not enough to detract from the storyline.
Anne McCaffry's Dragonriders of Pern series is an excellent fusion of scifi and fantasy. It's hard to recommend a specific one, since they're all good and most of them stand alone pretty well. The same goes for Peirs Anthony's Xanth novels, though I particularly liked Yon Ill Wind and Man From Mundania.
Hideyuki Kikuchi's Vampire Hunter D novels are more a three-way blend between horror, fantasy, and scifi (elements such as cyborg technology appear right alongside mutants, vampires, and sorcerers), but it's an excellent read. The one criticism I have of the series is that DH Press's translations of the first two books is rather stiff, but they get better by the third and flow more freely. Speaking of which, the third book, Demon Deathchase, is actually my favorite out of the series, followed closely by book six, Pilgrimage of the Sacred and the Profane.
If he's into comics, Neil Gaiman's Sandman series is worth a try, as are manga like Sorcerer Hunters, Those Who Hunt Elves, and Slayers.