The Journal of Patrick Breen, the only account of the Donner Party written during the ordeal. Online through the University of California's Online Archive.
Calabro, Marian, The Perilous Journey of the Donner Party, Clarion Books, New York, 1999. Easy to-follow version with many pictures and charts, principally meant for young adults.
Devoto, Bernard, The Year of Decision: 1846; Little, Brown and Company, Boston, 1943. Focuses on all general Westward Emigration in 1846, as well as information about the Westward Movement up until that time.
Hardesty, Donald L., The Archeology of the Donner Party, University of Nevada Press, Reno, 1997. An account of a more recent excavation of the Murphy Cabin and Alder Creek area.
Johnson, Kristin, Unfortunate Emigrants, Utah State University Press, 1996. Highly useful resource of the Donner Party featuring much various media and accounts by survivors and rescuers.
McGlashan, C.F., History of the Donner Party, C.F. McGlashan 1879 and 1880. The first full-length account of the Donner Party, now online.
Virginia Reed,(-Murphy) "Across the Plains in the Donner Party," Century Magazine, 1891.