Originally Posted by ahi
"Good Omens" by Terry Pratchett and Neil Gaiman
The Discworld series by Terry Pratchett--though I personally cannot appreciate the original English language version, but rather enjoy my Hungarian translations thereof.
"Things I and my girlfriend have argued about" by Mil Millington
Anything by P. G. Wodehouse.
hey ! somebody else who knows mil millington ! i love that guy ! i will strongly second this recommendation. his emails / columns / website are also hilarious, if you're interested.
also second wodehouse, of course. and jerome k. jerome. and i imagine you've read all the douglas adams books ?
mark twain is also really funny and you can get several of his books here.
i also love gerald durrell's books ("my family and other animals", etc.) but i'm not sure if they're available as ebooks (hm, i should check...).