Most American grad level math textbooks are as hardcore as it gets; undergrad, not so much, especially compared to such introductory texts as, say, Beginner's C

Most American grad level math textbooks are as hardcore as it gets; undergrad, not so much, especially compared to such introductory texts as, say, Beginner's Course in Topology: Geometric Chapters by Rokhlin et al. which, I’d say, is extreme in its hard-coreness. (A popular text by Munkres, by comparison, is a children’s book.)