Can I skip some Art of Problem Solving Books or do they build on each other so much that i would be behind?

Anybody know much about Art of Problem Solving? I'm trying to learn all the math I didnt learn in High School so I can get to calculus and go back to school to get a math degree and maybe a PhD in math education or potentially economics (my BA was in Econ but it never involved much math). Ive been using AoPS to learn the material, and have donr Prealgebra, Introduction to Algebra, Introduction to Counting and Probability, and I'm currently on Geometry. The next books in order are Introduction to Number Theory, Intermediate Algebra, Intermediate Counting and Probability, Precalculus, and then Calculus. It's taken me a year just to get to Geometry and I have 5 more books left and the Algebra 2 book alone is 800 pages and I'm wondering if anyone knows if I can just skip the Number Theory and Counting books and go straight to precalc once I finish Algebra, or if the material builds such that I would be seriously behind if I tried to skip books? Thanks!