Adventure — Anything by Jules Verne (20,000 leagues under the sea, around the world in 80 days). Read ‘em like crazy when I was younger.

Fantasy — Dragonlace is fun for younger readers. The Witcher is for those who want something a little grittier with a heroic protagonist.

Philosophical fiction — I first read Ayn Rand’s Anthem when I was 15/16. It’s still one of my favorite books.