And for you, NewSc2, I would suggest "Elementary Training for Musicians" from Paul Hindemith. He also wrote other books like Traditional Harmony, The Craft of Musical Composition, but just in case you want to write classical stuff. But that first one will give you a base for whatever you wanna be as a musician. Well, I know, there is a bunch of options out there, this is just one...
greetings,
macnando