Best UNIX intro text

[John Crane]

For the very raw beginner, I recommend the book by Yates.

For the moderately advanced person, I recommend the Bourne book "The
UNIX System". This is an excellence reference that I use every day.

After mastering Bourne, try Kernighan and Pike's book "The UNIX
Programming Environment". It made me a confirmed awk user. The difference
between this book and Bourne's book is that Bourne clearly explains
what the utilities are and lays out all possible options. This book
gives concrete examples and helps you build several useful tools.

The above books are not novels. Read them at the terminal and try the
examples.