You have all 3.5 edition books!
All monster manuals, all player handbooks, all DM guides!
ALL campaign settings Greyhawk, Eberron....with all their add-ons!
All the equipement books!
Legends & Lair collection
The Quintessential Collection!
The Slayers guide to collection!
All dungeon tiles and map folios!
Basically, I'd say its 99.9999% 3/3.5 edition material!
My fourth edition books are on another pc