Hoo, doggy! I'll do some judicious editing for the sake of bandwidth here.
Pretty much anything by Neil Gaiman, but "Murder Mysteries" is one of my all-time faves.
Ditto for Terry Pratchett, particularly "Good Omens" (I love that book so much I've given three of my own copies to other people)
And again for Christopher Moore, but I have to say that "Bloodsucking Fiends: A Love Story" will always hold a special place in my heart, but "Lamb: The Gospel According to Biff, Christ's Childhood Pal", and "The Stupidest Angel: A Heartwarming Story of Christmas Horror" are probably my favorites. …Erm, they're really not as blasphemous as they sound, in case anyone was looking at me all slanty-eyed. I just happen to think that Christmas stories could use more zombies once in a while.
"Howl's Moving Castle" by Diana Wynne Jones is another favorite. One of those rare books that a person of any age can truly enjoy.
The entire Vampire Files series by P. N. Elrod has been a consistant favorite of mine since I was about ten years old; I just never outgrew it and in fact go into happy conniptions every time she puts out a new book. I just love the idea of a smartass everyman vampire gumshoe who's admittedly squeamish about his eating habits.
The Harry Potter series by J K Rowling.
Pretty much anything by William Shakespeare, but favorites include "Twelfth Night", "MacBeth", "Hamlet", "Two Gentlemen of Verona", and "Much Ado About Nothing".
Anything by e. e. cummings, particularly the poem that starts "somewhere I have never travelled gladly beyond". My favorite poem of all-time.
"Alice's Adventures in Wonderland" and "Through the Looking-Glass" by Lewis Carroll have always been among my favorite stories and remain so to this day.
"The Boyfriend School" by Sarah Bird is delightfully witty and fun and I'm so glad I gave it a chance.
"To Kill a Mockingbird" by Harper Lee is another one that's been one of my favorites since I read it in high school.
"The Hitchhiker's Guide to the Galaxy" by Douglas Adams is another on my always-has-been favorites list, still makes me giggle like a lunatic when I read it. Gosh I love dry British humor.
The Myth-Adventures series by Robert Asprin is another one that's been with the faves since junior high when I discovered them. Still funny, still fun, still lots of adventure. I'm so glad he's started writing them again, I missed them.
Oh I could go on and on but I'll restrain myself.
Infinity Welcomes Safe Drivers
Better Than Life
Yes! The Red Dwarf books! I got ahold of those years ago and loved them and I really, really want to get ahold of the next two but I don't think they're available in the States for some reason.