Rarely does one encounter any scholarly book for which it can be said that the critical praise quoted on the back cover is fully justified. This is such a book despite the sadly misleading title and the grossly ill‐conceived index (which provides no simple way to trace any proper name or title and uselessly lists some as merely “passim”). The subject matter is the content of texts from the early Tang dynasty that have come to be regarded as a “school” called “Twofold Mystery” (Chongxuan). Assandri argues that its “most salient feature is a creative use of a technique of reasoning”—the tetralemma of the Indian Mādhyamika thinker Nāgārjuna. Yet it “relied on a distinctively Daoist worldview, starting with the premise that the indefinable Dao was ontological substrate and origin of being”—ideas familiar to Sinologists from the “Dark Learning” (Xuanxue/Hsüan‐hsüeh) “school” of such third‐century thinkers as Wang Bi (long known as “Neo‐Taoists”). Thanks to contributions by European scholars of the 1980s like I. Robinet and L. Kohn (publisher of Three Pines Press), Assandri can show readers today the depth and diversity of Taoist thought among such early seventh‐century thinkers as L. Rong (fl. 658‐83) and C. Xuanying (fl. 632‐50); contemporary texts such as the Huming jing (“Scripture of Saving Life”); and such eighth‐century texts as the Benji jing (“Scripture on Original Time”)—parts or all of which are translated in appendices. Assandri thoughtfully explores “the multi‐faceted philosophical interaction of Tang Buddhists and Daoists in a concrete and documented historical environment,” and all scholars of Chinese Thought or Religion should read her careful analyses. But any serious student will not only be vexed by an inability to find key data, but will labor with difficulty to understand the issues without plowing through the entire book and making one's own references.