Here are three books that are pretty good:

Hands-On guide to Oscilloscopes by Barry Ross
McGraw-Hill
ISBN 0-07-707818-7

The Complete Book of Oscilloscopes 2nd Edition by Stan Prentiss
Tab Books
ISBN 0-8306-3908-X

and

Troubleshooting with your Triggered-Sweep Oscilloscope by Robert Goodman
Tab Books
ISBN 0-8306-3891-1

I like Ross' the most for basic explanations.

GL!

Dino KLØS/4