""Cotton's Library"" reveals what can happen to a museum-quality collection before it reaches the safety of a museum (and sometimes even after). It is the story of an embryonic British national library assembled more than 400 years ago by Sir Robert Cotton. Boasting masterpieces of medieval illumination, the sole manuscript sources of Beowulf and ""Sir Gawain and the Green Knight,"" and two of four surviving 1215 copies of Magna Carta as well as many priceless historic records, Cotton's library was and is an irreplaceable treasure of the English-speaking world. Cotton and his successors nonetheless struggled for centuries to preserve his library for, and sometimes from, formal government custodianship. Overcoming war, repression, greedy heirs, intriguing rivals and disastrous fires, they ultimately succeeded, to our own great benefit. ""Cotton's Library"" tells how they did it.