You can find the information about textbooks here. Most of them will be freely accessible open-resources textbooks that cost you nothing from online.

The usual textbook for this class is:
Astronomy: A Beginner’s Guide to the Universe, Chaisson & McMillan, eighth edition (Recommended, not required)
But since it’s pricey, it’s not suggested that you purchase it.

An open-access textbook, linked below, can be used as your main source of texts in the course.
https://open.umn.edu/opentextbooks/textbooks/astronomy
The book covers much more topics than what’s planned for this course, so please refer to the syllabus for the selected chapters for the lectures. The rest can be reading materials for you.