Melvin Powers Course [which includes "How To Get Rich In Mail Order & Making Money With Classified Ads] was great.
Not only did the course give good information, the writing style was so friendly and movitvational . . . you felt like you couldn't help but succeed as you read it.
Tied for 1st is Jeffrey Lant's: How To Make A Whole Lot More Than 1,000,000 Writing, Commissioning, Publishing And Selling How-To Information
Lant's book has more information on the subject than any other I've ever seen [over 500 pages and the type is small!]
His writing style [and personality] is a bit obnoxious at times. That can be a drawback. But as far as the information goes, he really delivers.
Jimmy Krug
P.S. Melvin Powers is one of the few "Infoprenuers" who REGULARLY makes money selling products "besides" those teaching people How-To make money selling information.