The book contains a number of Easter Eggs - mostly codebreaking exercises. Try your hand at cracking a few of the codes - there is a $1000 award up for grabs. Or you could send out some emails - one never knows who (or what) will reply.
If you've found a code that isn't on the list of eggs discovered so far, please send it in! Credit will be given to the first few people who solve the eggs in question.
I've listed some resources - books, programming guides and the like - as a place to get started.