There are numerous books, articles and essays covering all aspects of the Hereford Mappa Mundi but Westrem is the indispensable reference work to which one returns again and again. Mappa is divided into sections and each legend or inscription numbered so that a translation and full explanation can be quickly accessed in the body of the work. There is an excellent introduction and a useful index. Anyone wishing to acquire a detailed understanding of the map will inevitably find themselves resorting to Westrem for the facts. Even this book cannot answer every question concerning the map but it does provide essential information without which discussion would be ill informed and pointless.