There aren't universally well-known books or courses that suit everyone studying math at this level, and the why is because everybody has their own needs.
What you are calling "lower-level math" includes everything that you might expect people could learn in primary and secondary education, from age 2 to age 16 - that's 15 years in which everyone takes their own path and ends up at a different place. It is specialized.
What you are calling "lower-level math" includes everything that you might expect people could learn in primary and secondary education, from age 2 to age 16 - that's 15 years in which everyone takes their own path and ends up at a different place. It is specialized.