Multiengine Flying, Paul A. Craig (McGrawHill)
POH's for each of the aircraft
Any study guides you want and obviously AFD's, Charts, Plates, Current FAR/AIM, etc....
Airplane Flying Handbook FAA-H-8083-3
Pilots Handbook of Aeronautical Knowledge AC 61-23C
Aviation Weather Services AC-45E
Aviation Weather AC 00-6A
Instrument Flying Handbook FAA-H-8083-15
I think thats pretty complete. I grabbed quite a few other texts for my library...
ASA Texts, Aircraft Systems for Pilots (Jepps), FARS Explained (Jepps) and some others.
There is an additional CFI list I can post if you want it.
The FSI bookstore prices on texts were not inflated. Unless you can find a good sale elsewhere they will be the same price at school.