Essays on Early Medieval Mathematics is part of the Variorum Collected Studies series, which reproduces papers directly from their original (sometimes quite obscure) sources, preserving even the original pagination. (This is intended to make it easier to trace references to the papers, but it does mean that we get a book that isn't as pleasant to the eye.)
These are research papers, not expository writing, but this book is worth having in your library, even if it is strictly an undergraduate library, because all too many histories short-change the period in question, suggesting that nothing interesting happened in the early medieval period in Europe. The very first essay in the book, called "The Importance of the Latin Middle Ages for the Development of Mathematics", deals with this issue directly. It would make a great reading assignment for a history of mathematics course.
The rest of the book is more technical; among other things, it includes editions and translations (not always into English) of important historical sources. Given the price, few people will want to buy themselves a copy, but libraries that aim to have a good collection in the history of mathematics should have this one.
Fernando Q. Gouvêa is Carter Professor of Mathematics at Colby College in Waterville, ME.
Introduction; The importance of the Latin Middle Ages for the development of mathematics; Mathematische Probleme im Corpus agrimensorum; De arithmeticis propositionibus. A mathematical treatise ascribed to the Venerable Bede; The Propositiones ad acuendos iuvenes ascribed to Alcuin; Die älteste mathematische Aufgabensammlung in lateinischer Sprache: Die Alkuin zugeschriebenen Propositiones ad acuendos iuvenes. Überlieferung, Inhalt, Kritische Edition; The names and forms of the numerals on the abacus in the Gerbert tradition; The importance of the Pseudo-Boethian Geometria during the Middle Ages; Die Altercatio in der Geometrie I des Pseudo-Boethius. Ein Beitrag zur Geometrie im mittelalterlichen Quadrivium; The Geometry II ascribed to Boethius; A treatise on the squaring of the circle by Franco of Liège, of about 1050; 'Rithmomachia', a mathematical game from the Middle Ages; Index.