Investigating the Mansion

Tony busted the door open to the empty mansion. The Gentleman was there before, but his sensors were being scrambled. He switched to normal visuals and continued to do a room by room search. Once he left the main hall area he found a comfortable living room, well stocked kitchen, and even an exercise room.

There were studies filled with books. A bunch of guest rooms all decorated in a variety of ways. Where should he check out first?