That's a fairly common error. The late Tommy Wonder made the same mistake in a set of lecture notes he used to sell for $15 that consisted of just a single page on red paper, folded in half, inside of which was a single paragraph which said:
"Dear Magic friend,
All I know about magic can be found in the following books:
Magic and Showmanship Dariel Fitzkee [sic]
Magic by Misdirection Dariel Fitzkee
Showmanship for Magicians Henning Nelms [sic]
These books tell you almost anything there is to know about magic. They give you an insight into what magic really is, which is far more important than knowing how my tricks (or anybody else's tricks for that matter) are done. At least these books have helped me a lot, may they help you as well.
Of course, he would include for free with the above notes a booklet called "Wonder Material" that did give the technical details of his tricks, but he stressed that this was just a free gift and fair less important than the above notes...