American Government 2eKrutz, G. (Ed.). (2019). American government 2e. Rice University.
https://openstax.org/details/books/american-government-2e
Read Chapter 3, 11 (section 11.5), Chapter 12 (section 12.5), Chapter 13 (section 13.5): These chapters deal specifically with all 3 branches of government and how there was a division of powers.