Geršgorin and His Circles

From the reviews:

"This book is an extremely detailed account of eigenvalue inclusion theorems, starting with the basic Geršgorin disk theorem … . One of the most pleasing features of the book is what Varga calls the first recurring theme: every eigenvalue inclusion theorem has a corresponding nonsingularity theorem. … contains numerous simple examples and illustrative diagrams, and everything is explained in great detail. … For anyone seeking information about eigenvalue inclusion theorems, this book will be a great reference."
(David Scott Watkins, Mathematical Reviews, 2005h)

"The monograph presents a survey of results about spectrum localization for matrices, beginning with the first Geršgorin’s eigenvalue inclusion result … . This book contains many new and some unpublished results as a survey of many Geršgorin type results in the literature. The presented material is almost entirely self-contained with exercises which are useful both for graduate students in mathematics and physicists, engineers and computer scientists."
(Boris V. Loginov, Zentralblatt MATH, 1057:8, 2005)

"The new book of Varga contains, along with several new results, nearly all that has been discovered about eiegnvalue inclusions since 1931. … One of the merits of this book is the information that it provides about Semën Aronovic Gersgorin … . I like this book and recommend reading it." (L. Elsner, American Mathematical Monthly, Vol. 113, April, 2006)