I was hoping someone would mention it! While it is a good book as well (and Kent Beck has many of them!) I tend to describe his book as 1st generation TDD. It certainly was a great breakthrough in 2002 but it misses some very good thoughts that only came later (and to give credit: probably only thanks to his book). So, GOOS for me is the 2nd generation of TDD. Especially part II is invaluable to give as a reading and thinking exercise for my new devs.