Francis of Assisi recovered an earlier strand of the Christian tradition through his rapport with the animal kingdom and his love of the created order, a moment captured by historians and artists such as Roger Wendover and Matthew Paris, monks of St Alban's Abbey. The saint's Canticle of Brother Sun celebrates the divine bounty within the realm of creation, enumerating four elements: fire, water, earth and air. The Franciscan order's interest in the realm of science and alchemy was noted by a number of its chroniclers, who also noted its Joachite interests. Commentaries on Hexaëmeron belonged to the incipient schools of Oxford and Paris through Robert Grosseteste and Bonaventure of Bagnoregio, as did the apocalyptic writings of Joachim of Fiore, the Calabrian abbot. Commentaries on the book of the Apocalypse enjoyed some popularity among English friars during the thirteenth and fourteenth century. Zachary A. Matus, a lecturer at Boston College, traces scientific writings within the Franciscan school, especially the writings of Roger Bacon, Vitalis of Furno and John of Rupescissa, three theologians interested in apocalyptic texts. While Roger Bacon's scientific writings are well documented, John of Rupescissa is a lesser known figure. The latter was quite forthright in his views on the unity of the order and made no bones about his disapproval of Angelo Clareno, Ubertino da Casale and Philip of Majorca, reformers who paved the way for the emergence and flowering of the observant tradition from the second half of the fourteenth century; he accused these friars of effectively splitting the order. One of the principal benefits of this study is the space allocated to a summary of John of Rupescissa's writings, especially his Libor ostensor. Matus seems to prefer the ideas of Bacon and John to those of the former minister provincial of Aquitaine and cardinal bishop of Albano. The volume opens with a full introduction and then divides itself into four chapters and a conclusion. It provides a sound introduction to the scientific interests of the early friars, whose studies were nurtured by the liberal arts and the natural sciences before advancing to theological studies. The order's legislation on the subject of alchemy is noted, as is ecclesiastical disapproval. The volume has a short index of fewer than three pages (pp.199–201). There are two typographical errors: ‘authors prior to Olivi as a a typical means of’ (p. 33) and ‘he is being granted knowledge a well as an experience more akin to mystical ecstasy’ (p.132). The University of Pennsylvania Press is to be congratulated on this handsomely produced volume which will be warmly welcomed by the growing community of scholars who wish to learn more about the scientific studies of the Franciscans in the Middle Ages as well as the order's apocalyptic tradition.