Taking one of your replies i guess i found your goals. You can touch other area's when you become more comfortable with the tools required, then try other sections of production and see which you want to take more advantage of over another then with artstation search for that topic and stalk someone's work that you want…
I'm not sure about books, but I've found a bunch of YouTube tutorials which have helped with composition a ton. https://www.youtube.com/watch?v=Qj1FK8n7WgY&t=842shttps://www.youtube.com/watch?v=O8i7OKbWmRM&t=1613s