Inside Jokes by Hurley, Dennett and Adams, Jr.
Inside Jokes is full of jokes, some hilarious, many not, but all used to illustrate their analyses of humour and why we have it. Their many thesis is that humour (or mirth) is a result of the realization of a false belief and this process is 'paid for' in evolutionary terms as the fitness advantage rewarded to the organism that (generally) maintains more accurate belief structures. Secondly, there is nothing intrinsically funny of humourous in stimuli, but in the brain of the person who is amused or laughing. They draw the parallel to the lack of intrinsic colour in the objects around you as well as in your head when you 'see' colour, as the perception/experience is a combination of outside stimuli being coded/decoded in a certain way by your brain.