IPA: /ˈskuːlˌbʊk/
KK: /ˈskuːlˌbʊk/
A book used for studying in school, often containing lessons and exercises.
I bought a new schoolbook for my math class.
Schoolbook → It is formed from "school" (from Old English *scolu*, meaning a place of learning) and "book" (from Old English *bōc*, meaning a written work or text). A schoolbook is a book used in a place of learning.
Think of a 'place of learning' ('school') where you use a 'written work' ('book') — that's what a schoolbook is.
No commonly confused words.