Bungie.net or halocharts.com. The Bungie site has everything you could want to know about your Halo career, all the way back to H2. Halocharts compares your stats in Reach to other players that have been to their website.
It is on a bookshelf near the guys you saved. The problem is that you have to get into her office first to scan her fingerprints (which lead you to the book). You have to climb through a vent to get into her office.