EE textbooks...to keep or not to keep?

So I am junior EE student and was wondering whether i should keep my upper level courses’ textbooks or not. I have my lower level courses’ textbooks simply because my brother will be coming in to TAMU in the future, but I’m confused as to what to do with my upper level books (rent or buy). Here are a list of my courses. I will obviously keep my elective courses’ textbooks, just not sure about upper level.

ECEN 214: Circuit Theory
ECEN 248: Introduction to Digital Logic Design
ECEN 303: Random Signals and Systems
ECEN 314: Signals and Systems
ECEN 322: Electric and Magnetic Field
ECEN 350: Computer Arch. and Design
ECEN 370: Electrical Properties of Materials
ECEN 325: Electronics
PHYS 222: Modern Physics
ISEN 302: Engineering Economic Analysis

Thanks!