Most likely you have never heard about this magic course. When I think about a 'magic gem' I have these 25 volumes in mind. This course could be called the 'British Tarbell Course' and in many respects it is much better than the Tarbell Course. It came out around the same time Tarbell issued his course and it had the same intent, to take a novice, introduce him to magic in a serious and thorough manner and give him all the information to develop him into a performer who can earn a living from performing magic. Rupert Howard's course does not cover as much ground as the Tarbell on trick technique, but quantity is not necessarily equal to quality.
Rupert Howard whose real name was Stuart Raw thought this course through extremely well. Let's start with the production values. The 25 volumes are large format volumes measuring almost 9.5" x 12" (larger than letter size). The covers are color covers and the inside paper is high quality glossy paper. Howard uses both photos and illustrations wherever most appropriate. There is lots of space on the side and sometimes on the bottom of pages for student notes. The structure of his instructions is very methodical and pedagogical. For example he doesn't simply start to explain tricks but rather with

Professional Attitude
Scientific Principles
How to Study
Your Success in Magic
Howard also adds a bit of magic history spread out through the first lessons - not too much to overwhelm the beginner but enough to keep you interested and teach you some of the most important historical facts.
It covers all major forms of magic from cards, coins, ropes, silks, balls, paper, cigarettes, thimbles, Mentalism, illusions, escapes, and all the essential parts of the business from marketing to the appropriate dress and attitude.

The 25 lessons are:

Easy Magic
Presentation and Paper Magic
Showmanship & Impromptu Magic
String and Rope Tricks
Sleight-of-Hand with Cards
More Tricks with Cards
Advanced Card Magic
Sleight-of-Hand with Coins
Handkerchief Magic
Cigarette Magic
Billiard Ball Manipulation
Thimble Magic and Watch Tricks
Egg Tricks
Productions and Opening Effects
Liquid and Chemical Magic, Tricks with Live Stock
Comedy Magic
Mental Phenomena
Spiritualistic Tricks
Miscellaneous Magic
Oriental Magic
Stage Illusions
Publicity Feats and Escape Tricks
Sensational Illusions
The Business Side of Magic
More Miscellaneous Magic