Athelstan was one of the first English kings, but nobody seems to have heard of him today in contrast to other kings of around his time such as Alfred The Great and Athelred the Unready. He achieved a big victory in 937 at an, as yet unconfirmed, location which secured the current kingdom of England for future generations.
Not much is actually know of him apart from what can be derived from the remaining fragmentary sources. Novertheless the book is quite infomrative and gives good background information on this period. Readers expecting a biography of Athelstan should note that this is note such a book; rather it gives an overview of events from roughly the time of Alfred the Great to the early 11th century, albeit that there is a focus on Athelstand's time (he died in AD939).