Then there's Allen Strange's book, Electronic Music: Systems, Techniques and Controls, which has been discussed here previously. Don't try to buy a real copy at the moment, unless you have some serious money to burn, for example here or vaguely cheaper here. As many have said on this forum, and elsewhere, this is an excellent and detailed book. A few forum members can probably make a pdf available upon request.
Allen Strange's book is more demanding, but also very rewarding, and just an hour sitting with it will create ideas that you'll be itching to make real - all IMO, of course If applied carefully, it could easily become the basis for a number of Patch Challenges.