I'm currently reading a new book, Queen Emma and the Vikings by Harriet O'Brien. It's about Emma, the Norman noblewoman who married first Aethelred, and then, after his death, Cnut/Canute. She was the mother of Harthacnut and Edward the Confessor, and also the indirect source of William's claim on the throne after Edward's death.

So far it's decent, but involves some supposition on the author's part, and is more of a general history of the early 11th century with Emma as its linchpin than a specific biography of her. I don't know if O'Brien has training as a historian. Her biography makes her look like a journalist and does not say what her academic qualifications are.

My favorite bit so far is the accounts (there are several) of Cnut's execution of Eadric Streona, which seems to have followed pretty closely on Eadric's brutal murder of Aethelred's son Edmund Ironside. Eadric had what can best be termed as an eye for the main chance, and whether Cnut supported Edmund's murder or not (it certainly benefited him), he knew better than to trust Eadric.