From the reviews:

"The book under review is a collection of selected papers by Ennio De Giorgi (1928-1996). … The book has been very carefully prepared and printed. It is a valuable source for all interested in the work of De Giorgi. It presents the broad range of his achievements and his entire intellectual path, as a problem solver and as a proponent of deep and ambitious mathematical theories." (Roman Murawski, Zentrablatt MATH, Vol. 1096 (22), 2006)

"This volume contains a well-balanced choice of papers written by Ennio De Giorgi, an outstanding Italian mathematician of the 20th century. … In my opinion the volume, which covers all the main directions of the author’s activities (measure theory, the 19th Hilbert problem, minimal hypersurfaces, G- and D-convergence, and foundations of mathematics) should be on the shelves of every mathematical library." (EMS Newsletter, December 2006)

Ennio de Giorgi (Lecce, February 8, 1928 – Pisa, October 25, 1996) was an influential 20th century Italian mathematician. He made important contributions to mathematical analysis, in particular to the study of minimal surfaces and to the regularity of the solutions of elliptic partial differential equations. One of his major contributions to the latter was to solve the 19th Hilbert problem, which John Forbes Nash solved independently at roughly the same time. His work has influenced Luis Caffarelli and many other mathematicians.