You may not like this, but I suggest another complicated dimension be applied like learning style. A concrete example of what I'm taking about is some people learn the quicksort best in prose / analogy, some learn it best in psuedocode, some learn the best in whatever language they are most comfortable in, and some would learn the best from graphical animation flowcharty type things. So its entirely possible the path to mastering the quicksort would be four different books for four different people. Of course you can "fix" that by simply having different paths to the same goal for different learning styles.
Even worse is people playing their own multidimensional games when mushed up against a multidimensional book. So is the little schemer series really a book about learning scheme or a book about learning programming or purely educational learning how to think? One book could quite easily end up in three totally different linked list / tree diagrams that you're proposing.
Purely from a startup business strategy idea, I suppose you have a guaranteed sale to some bookseller or another.
http://www.inference.phy.cam.ac.uk/itprnn/book.pdf
Referenced table on page six of the PDF.