Another book I have been working my way through lately has been "The Joy of Quiz" by Alan Connor. Alan works on Only Connect and you may have heard him on radio, or read in various newspapers, his promotion of this title. After reading the book over the last week, I would highly recommend it no matter how serious you take your quizzing. From the story of Trivial Pursuit to a look at the modern quizzing scene it covers everything. (See link below)
In addition, if you like the above title, then one book definetly worth reading (and available for pennies from Amazon) is the "Brain Men" book from Marcus Berkmann. Another great look into the "serious" side of quizzing written in a very entertaining manner..