It looks like a wonderful book, Tom. You're right that there's often too few books between References/Handbooks/RFCs and "This is how you click a button!". I'm sure it'll help a lot of people.
If I could make one stylistic suggestion: A little bit of whitespace or a tab indent at the start of a paragraph (e.g. the first section of the Primary Master Name Server section on p.118 of the sample) would help the eye. There's good use of whitespace in separating commands or file contents from discussion, etc., but when several paragraphs are together it seems like no whitespace is used.
I'll probably snag a copy in a few days. Best of luck with it!
Cheers,
Scott.