The other benefit is that all of the AoPS books have extremely complete solutions manuals so you'll get immediate feedback on the quality of your solution, or you can just look if you've been banging your head against something for a while. Solutions manuals are the autodidact's best friend. Other high quality books with complete solutions included or in separate solutions manuals include Spivak's Calculus, Hubbard and Hubbard's Vector Calculus, Tenenbaum and Pollard's Ordinary Differential Equations (a really cheap Dover text from the 60s!), and Knuth et. al's Concrete Mathematics. Going through the AoPS books and the above will give you an extremely solid foundation to learn any further math you might need as a software engineer as needed. If you have a career spanning 3-4 decades, spending a few years mastering this material can be extremely useful.
Also recommended in this reply