By A+T Research Group (Aurora Fern'ndez Per, Javier Mozas, and Alex S. Ollero). A+T Architecture Publishers, June 2013, 496 pages, $53. European Lessons for Living This handsome and valuable compendium of social housing projects in Europe is actually three books: a chronological presentation of 10 projects tracing the development of architectural concepts for collective housing from 1919 to about 1970; a superlative example of how well-organized and stunning graphics can allow for comparisons between projects; and a manifesto for promoting humane high-density living. The authors, who are also the publishers, are members of a group formed in Spain in 1992