The work of an historical theologian, this study puts the ideas and experiences of the Dominican friar and missionary Riccoldo da Montecroce (d. 1320) into dialogue with contemporary Christian theology of religions, noting in particular that Riccoldo's frequent invocation of his experientia living among Muslims anticipates the important role of direct experience of the other as an authoritative source in the theology of religions, experience that can be – as it certainly was for him – destablising and painful. Focusing on his Liber peregrinationis, which recounts his wide travels and long sojourn in the Middle East, and his Epistolae ad ecclesiam triumphantem, an utterly unique Jeremiad on the final defeat of the Crusader States in 1291, George-Tvrtković devotes the core of her study to three themes of these works that collectively shed light on what she calls Riccoldo's ‘nascent theology of Islam’: his quite authentic admiration for Muslim piety and practice; his repeated stress on his direct access to the Qur'an in Arabic, a language that he knew very well; and his impassioned doubt, expressed in the latter work, that God truly favours Christianity and apparent willingness to convert to Islam if God made it clear that ‘Muhammad should reign’. The work of an excellent Latinist and meticulous scholar, A Christian pilgrim is lucidly written and compelling in its argument that, while Riccoldo was not primarily a theologian and wrote no truly theological works, we can discern in his works the elements of a Christian theology of Islam characterised by ‘wonder, doubt, and dissonance’, a theology that, she urges, modern theologians should attend to. As she makes clear, Riccoldo did not remain in this wondering and doubting theological posture throughout his life. Indeed, we find him later, back in Florence, writing the most widely read polemical attack on Islam of the late medieval and early modern periods. The theological dimension of her study might have been enriched by fuller reflection on the definitive closing of Riccoldo's opening to wonder and doubt – what lessons there for modern theologians of religions, whatever tradition they represent? Historians will find here the fullest presentation of Riccoldo's travels and thought in the English language, a presentation informed by both wide reading in the modern scholarly literature on Riccoldo and Dominican mission in the Middle Ages, and a balanced and careful use of the sources. The second half of the book consists of the author's English translations of the Liber peregrinationis and the Epistolae (the first such translation in each case), and these are of great value in themselves – indeed, anyone teaching courses on Christian-Muslim relations should add her English version of the Epistolae to the reading list immediately: their students will be astounded.