... You'd be wise to start reading Stephen Fry also. Actor, comedian, and oooohhh, a couple books that would be anyone else's total career. They've got quite a range on them, so here's a quick look (through my own biased lens) at how a few stack up.
Personally, I'd start with The Hippopotamus. I can say without reservation it's one of the finest reflections on the nature of faith and the value of skepticism ever written. It's also funny as hell. Filthy, insightful ... just, damn. This is going to sound weird, but I think the protagonist, Ted Wallace, is Spider Jerusalems' big, fat gayish drunken great-uncle. Read it and see.
The Liar is his first novel. It's a big, rambling bastard, with all sorts of meta-narrative tricks rippling through it. Sometimes a bit too clever for its own good, but in those cases you just have to stand back and marvel at the big brain at work here. Part roman a clef, part (intentional, I think) riff on Kingsley Amis' Lucky Jim.
Making History is his alternative history book. Very smart in spots, some nice twists -- what makes it work is that the high concept is basically just a tool Fry uses to tell an interesting story about self-discovery and love. Hard core science fiction fans might feel a little "been-there, done-that", and I can't argue with them. It hasn't held up for me, I'm afraid.
Moab is my Washpot is Fry's autobiography. A lot of what goes on in here has to be viewed through the lens of The Liar ... or vice versa. What Fry does here is really hang a series of sickly funny essays and observations on the coatrack of his life, from teenage runaway to prison to Cambridge University. Somehow, he makes that very unique little trip relatable to teenage angst everywhere.
Revenge is Fry's take on The Count of Monte Cristo. He changes style radically in the center of the book, and I like it. A fine read -- it hasn't had a chance to sit with me like the others have, so I can't fall behind it as passionately as I can The Hippopotamus. We'll see how I feel in a year, on the reread.
Now go spend the gift certificates you got.