At the very bottom of the sidebar, I have added links to some of the excellent books on medieval history by French medievalists and theologians. They include a book on St. Thomas Aquinas by Father Jean-Pierre Torrell, O.P., a new book by the great French medievalist Pierre Riché, an award winning, detailed biography on St. Bernard of Clairvaux by medievalist Pierre Aubé, and books by theologian/historians Jean LeClercq, Henri Marrou, and Henri de Lubac. It also includes Pierre Riché's survey of the great developments in the history of Western Europe around the year 1000 (including church, state, music, women, monks, bishops, and art of that era), and a recent translation of Boethius's Treatise on Music (a book that was very influential on the medieval study of music, which I do not think is available in English translation).
For English language books, there are already many links in bibliographies provided at the bottom of the short biographies (see the "biographies" category in the sidebar). There is also a Library Thing link in the sidebar, with links to more than 30 books that may be of interest to people who are thinking of becoming Catholic.