tl;dr
Is there a good theory book to go by that covers (in the same chronological order) the concepts in "Problems in Mathematical Analysis" by Demidovich?
details
I have about 3/4 of a year before I go to college and I'd like to complete Demidovich's book by then. I'm an ardent studier, and if need be, can work on math for 4 hours a day (the rest of my day is saved for other subjects), 6 days a week. I'd prefer a "rigorous" book, but not to the extent of Courant's "Introduction to Calculus and Mathematical Analysis".