John Asser was a Welsh monk at St. David's in Dyfed (southwest Wales). We know little about him until he was recruited by Alfred to join his court for his scholarly abilities.
In the biography, we learn that Alfred decided on St. Martin's Day in 887 (November 11) that he wanted to learn Latin, and asked Asser to be his teacher. Asser asked for six months to consider, since he did not want to leave his position at St. David's. This was granted, but Asser fell ill when he returned to St. David's, and a year later Alfred to ask why the delay. Asser said he would decide when he recovered. The monks at St. David's felt the arrangement could be beneficial to them, and Asser agreed to divide his time between the two obligations.
Asser mentions reading to Alfred in the evenings, meeting Alfred's mother-in-law, and traveling with him. He describes the geography of his travels in England, as if he were writing for an audience unfamiliar with the English countryside: possible for his Welsh countrymen, whose he wished to educate about the king. He also includes some anecdotes that help flesh out information otherwise found in the Anglo-Saxon Chronicle.
The biography does not mention any events after 893, although Alfred lived another six years (and Asser well beyond that). That fact, and the fact that there is a single manuscript, suggests that what we have is merely an early draft that never was finished and sent to be copied and distributed. On the other hand, there are other literary works that show evidence of access to Asser's manuscript. A history written by Byrhtferth of Ramsey in the late 10th century quotes large sections of Asser. An anonymous monk in Flanders seems acquainted with Asser's work in his 1040s-written Encomium Emma (Latin: "Praise of [Queen] Emma"). In the early 12th century, Florence of Worcester quotes Asser in his chronicle. It seems clear that Asser's manuscript either "made the rounds" or lived in a much-visited library; we just don't know where it was in its earliest existence.
We do know that Bishop Matthew Parker (died 1575) possessed it in his library, but it was not included in the catalog when he bequeathed his library to Corpus Christi, Cambridge. Prior to that, it was owned by the antiquary John Leland in the 1540s. He might have acquired it when Henry VIII dissolved the monasteries, salvaging it when their properties and possessions were being sold off.
I seem to have turned a life of Asser into a discussion of his one known piece off writing.
As a reward, and possibly to keep Asser from going back to Wales, Alfred gave him the monastery of Exeter. He was made Bishop of Sherborne sometime between 892 and 900. He may have been a bishop already, at St. David's.
In 1603, the antiquarian William Camden printed an edition of Asser's Life in which he ascribes to Asser the founding of a college at Oxford. This extraordinary and evidence-free claim was repeated, but no modern scholar or historian.
The Annals of Wales (probably kept at St. David's) mention Asser's death in 908. The Anglo-Saxon Chronicle entry for 909 (or 910, in some versions; different chroniclers started the year at different dates) tells us "Asser, who was bishop at Sherborne, departed."
And now for something completely different: one of the anecdotes he tells is about a daughter of King Offa, who married a king of Wessex and became a stereotype of Disney films: an evil queen. Tomorrow I'll tell you about Eadburh.
