I wrote an ebook 2 months ago on Awk called "Awk One-Liners Explained."

http://www.catonmat.net/blog/awk-book/

It teaches Awk through many practical examples, so called one-liners, that are small and short programs that just do one task. Such as joining lines, printing lines matching a pattern, summing up numbers on lines, converting text, etc.

Check it out!