Living Book for British History/Literature Class

I am teaching a high school British Lit class this year and would like to use a living book (rather than my literature textbook) to introduce students to the historical context of each work. So, for the Anglo Saxon period (Beowulf, the Ballads, etc.) I would like a resource that can introduce the history of that time in a well-written and interesting way. My budget is small, so I am hoping for one book! Anyone have any suggestions? Thank you!