This book represents the next in a long line of monographs written over the years on the topic of H-bonds, but one that takes a unique perspective. The authors have developed their own ideas of a unifying theme, intended to categorize all Hbonds in a systematic fashion, which they expand upon here at some length. At the same time, they do not limit themselves entirely to their own ideas, but spend some time reporting the history of how H-bonds have been conceived through the years. Chapter 1 offers a comprehensive list of earlier treatises and reviews on the subject, a useful service to the community. Chapter 2 classifies H-bonds mainly along the lines of the particular atoms (e.g., O, N, C, or metal) that are involved, or the strength of the interaction, but also introduces the authors’ division into six ‘‘chemical leitmotifs,’’ which relate to the phenomenological origin of stabilization, displaying some care to point out the weaknesses and limitations of each scheme. The reader may note a propensity to focus on crystal data in particular, easily understood in view of the large amount of such information available in the literature.