New Catholic Encyclopedia, Reference, BX 841 .C25 2003 v. 1-15. Use this to learn the Catholic viewpoint on medieval topics.
Oxford Dictionary of the Christian Church 2005 edition online. Oxford Dictionary of the Christian Church, Main BR 95 .O8 1997. The finest one volume reference work in any language on a single religion. Over 6,000 entries, on people, saints, places in Christianity in Europe and Britain, topics, glossary. Many bibliographical references.
Oxford Companion to Christian Thought, Main BR 95 .O84 2000. Longer entries than the Oxford Dictionary just above, but not as many. Briefer bibliographies. A guide less to facts than to the movement of ideas. Survey articles on historical periods, regions, national traditions. Articles on individuals and religious orders.
Encyclopedia of Early Christianity, Main BR 162.2 .E53 1997 v. 1-2. 1,245 entries cover from the life of Jesus to the 7th century. Entries for persons, places, doctrines, practices, art, liturgy, heresies, schisms. Brief definition, identification, or characterization followed by antecedents to the subject and chronological or topical development of the subject in early Christianity. Main patristic sources used are listed at end of article.
Historical Dictionary of Medieval Philosophy and Theology Main B 721 .B77 2018
Medieval Folklore: an Encyclopedia of Myths, Legends, Tales, Beliefs, and Customs Main GR 35 .M43 2000 v. 1-2
Over 300 entries on a wide variety of topics: customs and activities, religions beliefs (Christian, Muslim, Jewish, Pagan), oral and written literature, music, art, holidays, plants, animals. Entries are one to several pages. Illus. Further reading references. Signed entries. Three indexes, one of tales, one of motifs, and a general index.
Encyclopedia of Medieval Pilgrimage Main BX 2320.5 .E85 E53 2010
435 signed entries from over 180 scholars. Entries are a page to two to three pages each. Further reading references. Entries for local pilgrimage sites, shrines, wells, relics, as well as main pilgrimage routes, illustrate aspects of medieval society, from book production to the trade in relics, to the development of towns, art, architecture, literature. Dates covered: 300-1500 A.D.
Encyclopedia of Monasticism, Main BL 631 .E63 2000 v. 1-2. A conspectus of monastic life, past and present-its practices, doctrines, lifestyles, spiritualities and art. Articles on persons (founders, reformers, scholars, mystics, etc.), places (monastic histories of countries, cities, and individual institutions), Roman Catholic monastic orders, and themes (historical, sociological, theological, liturgical, gender, artistic, musical). Signed articles range from a page to several pages in length and include bibliographic references.
Explores the phenomenon of the Crusades in all of its complexity, ranging from the classic numbered crusades in the Middle East to the Reconquista in Spain, and from the Baltic Crusades to the crusades against Albigensian heretics in France. Entries for people, places, events, institutions, literary and historical sources, and themes.
Historical Dictionary of the Crusades Main D 155 .S53 2013 Authored by a professor of European history and the Crusades at Whitworth College in Spokane, Washington, who has published on crusade charters and on church reform in the 11th and 12th centuries. Has entries on people, topics, places, concepts, mostly a page or so in length. An overall bibliography is at the back, organized by place written about and the individual crusades.
Latourette, History of Christianity, Main, BR 145 .L28 c. 2. A text on the history of Christianity, for reading up on the topic. See esp. pp. 269-688, which cover from 500 to 1500. Many chapters cover various topics of medieval Christianity: monasticism, popular religious movements, thought, parish life, public and private worship and devotion, the crusades, efforts to revive and purify the Church at various times.
Palgrave Dictionary of Medieval Anglo-Jewish History Main DS 135 .E5 P35 2013 Covers approximately 1136-1290. Contains an overview essay, statutory and other key documents, and topographical, biographical and general entries. The entries variy in length. Extensive bibliography. Illustrated.