This translation of book v of the very large Rationale divinorum officiorum of the French bishop (of Mende) and canonist William Durand (d. 1296) is very welcome. Working from the Latin text (of all eight books), as co-edited by the late Dom Anselm Davril and Timothy Thibodeau, in the Corpus Christianorum Continuatio Mediaeualis series, Thibodeau has now produced translations, with a regrettably confused sequence of publishers, of Durand's bk i (New York 2007), bks ii and iii (Scranton 2011), and bk iv (Turnhout 2013), previous to the volume under review. Durand's bk v is an extended and systematic presentation of the daily office, beginning with discussion of the constituent parts in general (hymns, lessons, responsories etc.), followed by treatment of each service, from the Night Office to Compline. The tenor of Durand's commentary is a mixture of sober exposition and figurative explanation (remorseless sometimes to the point of absurdity: for example, ‘The sign of the cross must be performed with three fingers because it is imprinted with the invocation of the Holy Spirit … But the thumb has preeminence over the other two’). Durand's awareness of some diversity is notable; unfortunately, instead of specifying where the variations he notes are used, he resorts to the general ‘in many churches’, ‘in some churches’, and the like. Thibodeau's translation is usefully straightforward (there is one seriously misleading transposition at pp. 67–8, 80, where ‘signing’ should be ‘singing’). The introduction offers a brief but surprisingly complete discussion of the history of the office, making plain the distinction between monastic and secular (which he calls ‘cathedral’) forms. The annotation is thorough without being overwhelming, as is appropriate for this series of translations, plainly intended for the use of students, who are fortunate indeed to have this resource at their disposal.