Douglas Adams!! specifically these five by him:
The Hitchhiker's Guide to the Galaxy
The Restaurant at the End of the Universe
Life, the Universe, and Everything
So Long, and Thanks for All the Fish
Mostly Harmless
they are laugh out loud funny - i have read The Hitchhiker's Guide to the Galaxy a few times (5 or 6 maybe?) and it makes me smile so much that by the end of the book the sides of my mouth hurt