The Anglo-Saxon Chronicle is a collection of annals in Old English chronicling the history of the Anglo-Saxons. The original manuscript of the Chronicle was created late in the 9th century, probably in Wessex, during the reign of Alfred the Great (r. 871–899). Multiple copies were made of that one original and then distributed to monasteries across England, where they were independently updated. In one case, the Chronicle was still being actively updated in 1154.
The Anglo-Saxon Chronicle is an invaluable resource for anyone studying the history of England. It is definitely not light reading, but it is filled with fascinating and intriguing details of life in England before to just after the Norman Conquest.
Michael Swanton's edition of the Anglo-Saxon Chronicle is a good, handy reference in modern English. A group of manuscripts (eight in all) rather than a single unified book, the Chronicle is the first continuously-maintained vernacular national historical work in Western history. Swanton has here translated and edited the manuscripts to form a continuous whole, and included extensive notes.
A good successor to Garmonsway's parallel translation of the various Chronicle texts - good translation, ample notes, solid introduction. It also has good maps and supplementary material for the history.