The bookshops Campusbokhandeln and Akademibokhandeln in Uppsala are both physical stores that offer course litterature. You can borrow many books at the university and student nation libraries. Online bookshops, like Adlibris and Bokus also sell course literature.
Some of the required reading can be compendiums that are sold by the teacher at the start of the course or in the departmental office. Please note that course material bought from the department can only be paid with Swish. Compendiums for many courses are available in the student portal.