Rating: - reliable reference
I sure hope you don't intend to read this cover to cover. It functions best as a reliable and comprehensive reference to unix. For both system administrators and programmers. Yes, if you are the latter, you still have to deal with the operating system, even if you hide inside a programming language most of the time.

The various unix shells are evenhandedly described. The Bourne shell. The c shell. Korn shell. Try not to get into arguments with unix fans over the choice of shell. It is better to regard these as equivalent in functionality, with only minor differences not worth arguing about.

As the book explains, there are several unix variants. But the coverage spans all the major types. You can also use the book profitably if you have a linux machine. Most of the linux commands are deliberately mimicking unix equivalents.