IF Judaism, Christianity and Islam have no little in common in spite of their deep dogmatic differences, the spiritual content of that common element can best be appreciated in Jewish, Christian and Islamic mysticism, which bears equal testimony to that ever-deepening experience of the soul when the spiritual worshipper, whether he be follower of Moses or Jesus or Mohammed, turns whole-heartedly to God. As the Quest Series has already supplied for the first time those interested in such matters with a simple general introduction to Jewish mysticism, so it now provides an easy approach to the study of Islamic mysticism on which in English there exists no separate introduction. But not only have we in the following pages all that the general reader requires to be told at first about Sūfism; we have also a large amount of material that will be new even to professional Orientalists. Dr. Nicholson sets before us the results of twenty years’ unremitting labour, and that, too, with remarkable simplicity and clarity for such a subject; at the same time he lets the mystics mostly speak for themselves and mainly in his own fine versions from the original Arabic and Persian.