I call to your attention our new book: "Memory Evolutive Systems: Hierarchy, Emergence, Cognition", by Andrée Ehresmann and Jean-Paul Vanbremeersch, published in Elsevier's Series on Multidisciplinarity (Volume 4, 2007). This book, based on a 20 years long series of papers, develops the theory of Memory Evolutive Systems which we have introduced as a mathemati-cal model, based on category theory, for complex natural systems, such as biological, social or cognitive systems. It shows how well-known categorical operations (in particular (co)limits, partial completions of categories and fibrations) give an approach to the problems of hierarchy, emergence/reductionism, self-organization and learning. The main tools are exposed in Part A (Hierarchy and emergence), the global theory in Part B (Memory Evolutive Systems), and Part C (Applications to cognition and consciousness) is devoted to the case of cognitive systems, studying the formation of a procedural and a semantic memory allowing for the emergence of higher cognitive processes up to consciousness. The book is written for a multidisciplinary audience, with many illustrative examples in the most varied domains, but also with short proofs of the main mathematical results. An animation can be found on the internet site: http://perso.wanadoo.fr/vbm-ehr/ Comments and critics will be most welcomed. Andree Ehresmann