I think I have read some really funny books....but, at the moment, I have to say the Stephanie Plum Series by Janet Evanovich. They are numbered....one for the money, two for the dough, three to get deadly, etc. etc. I am reading number 18 now (explosive eighteen) I think it is the lastest. . I think the first 3 or 4 in the series, as you are getting to know the characters, are the hands-down funniest. Stephanie New Jersey bounty hunter by necessity and not very good at it....it is funny.
The other is almost anything by Robert Fulghum.... The All I Really Need to Know I Learned in Kindergarten and Maybe (Maybe Not) are my favorites. He is funny while leaving a lasting message.