Wow, 13 books ... that must've cost a fortune?! I had 9 books this semester and it cost me $500 total, the most it ever has

Good luck with all of the classes! 18 months straight is brutal, I did 4 semesters straight with no break (except for the obvious holidays) which was around 12 months, and it was tiring. I'm sure you will do fine though, your classes will probably be very interesting!