From the reviews: "This text provides a broad overview of topics related to non-classical consequence operators, nonmonotonic inference and belief change. The presentation is abstract and precise, and is grounded in a formal setting of logic." (Miroslav Truszezynski, Mathematical Reviews, Issue 2002 b) "The author does not merely present a digest of work that has already entered the mainstream. He gives the subject an individual shape based on concepts that he has himself developed in a series of recent papers. ... In brief, the book is based on a novel and coherent vision, developed according to a definite overall plan to yield non-trivial results ... ." (David Makinson, Zentralblatt MATH, Vol. 977, 2002)