Book In-Jokes in...
Advanced CORBA Programming with C++
Michi Henning and Steve Vinoski
(Addison Wesley, 1999)
Shortly after the book was published, the authors announced a prize-bearing Easter Egg hunt. The announcement only specified that the book “contains two Easter eggs, personally planted by Michi and Steve”.
As it turns out, the eggs were not found before a additional hint was published. This isn't surprising -- the eggs are certainly not something you will find on a casual read of the book.
Special thanks to Sergiy Matusevych for pointing my attention to this.