Brian Kernighan provides an enjoyable read detailing the creation of Unix.

I really enjoyed the "behind the scenes" stories that describe the whys & hows that led to the development of some of the programs and tools we use to this day, such as: pipes, grep/egrep, the C language itself, the Bourne shell, Make, Sed & Awk, and on and on!

The mini biographies of the many talented folks (e.g., Ken Thompson, Dennis Ritchie, Doug McIlroy) who were instrumental in creating Unix was a fund read as well.