1066 and All That by W.C Sellar and R.J Yeatman 

This book is short -- I got through it in a two hour break between classes without even having to check it out of the library -- and definitely worth the time it'll take you to read it. If you know some British history, even just the big things, it's all the better, but if you don't, you're really not missing out on any of the jokes. Very, very, very funny.