In William the Conqueror, Professor Douglas analyzes the causes and the true character of the Norman impact upon England in the eleventh century. The work is both a study of Anglo-Norman history and a biography of a man whose personal career was spectacular, and as reviewers have remarked, it is distinguished by a wealth of scholarship linked to a lucid and agreeable style.
Personally, I found the chapters on the church the most boring and the military and political information most interesting, but that likely just shows where my interests in medieval history lie and doesn't reflect on the quality of the writing in the various chapters. You may find yourself skipping one chapter or another to get to the parts you're interested in. The good news is that Douglas gives you all the information you could possibly want in each section and separates those sections clearly so you know what you're getting into. I would recommend this to anyone interested in history who has the patience for something a little closer to a textbook than the kind of histories you find on best-seller lists.