This book provides much detail on the changes involving the grammaticalization of personal and relative pronouns, topicalized nominals, complementizers, adverbs, prepositions, modals, perception verbs, and aspectual markers. It accounts for these changes in terms of two structural economy principles. Head Preference expresses that single words, i.e. heads, are used to build structures rather than full phrases, and Late Merge states that waiting as late as possible to merge, i.e. be added to the structure, is preferred over movement. The book also discusses grammar-external processes (e.g. prescriptivist rules) that inhibit change, and innovations that replenish the grammaticalized element. Most of the changes involve the (extended) CP and IP: as elements grammaticalize clause boundaries disappear. Cross-linguistic differences exist as to whether the CP, IP, and VP are all present and split and this is formulated as the Layer Principle. Changes involving the CP are typically brought about by Head Preference, whereas those involving the IP and VP by Late Merge.

Brady Clark, Northwestern University, in Studies in Language 32(1), 2008:
The Rise of Agreement is a substantial contribution to recent literature (e.g. Roberts & Roussou, van Gelderen 2004) that attempts to bridge the divide between formal and functional accounts of grammaticalization phenomena. The empirical scope of the book is wide, covering Bavarian, Rhaeto-Romance, Uto-Aztecan, Mongolian, and other languages. Fuß proposes a novel theoretical model of the creation of new agreement morphology. The book will be of interest to both historical morpho-syntacticians, as well as syntacticians interested in the structure of agreement.