There is a crisis in the archives. Contemporary protocols for archiving and accessing increasingly vast amounts of materials present unprecedented possibilities and problems for the production, classification, and use of knowledge. Surveying the jagged edge between memory and forgetting, revealing the force and scope of some of memory's losses -- its technical drop-outs, its lacunae, burials, omissions, eclipses, and denials -- Lost in the Archives explores the thesis that memory is productively read from its failures and absences, in the not-yet or impossible archives, in archive fevers and dementias, in all the places archives cannot or have not looked. Like a purloined letter, the shelved and forgotten book wields its most virulent power precisely in being unread. Unread, if not indeed illegible, what is lost in the archive may prove to exert the most shocking force.