Thorstein of the Mere is an adventure novel set in 10th-century England. The protagonist, Thorstein, is a young Norse settler who must navigate the dangerous world of shifting alliances and wars between Saxons, Britons, and Norsemen. The book is set in the Lake District of England, and Collingwood draws on his knowledge of the area to create a vivid and realistic setting. The story is appropriate for younger listeners, and older listeners will appreciate the historical insights it offers.