Eigenvalues in Riemannian Geometry: Volume 115 by Isaac Chavel (Dept. of Mathematics, The City College of the University of New York)
The basic goals of the book are: (i) to introduce the subject to those interested in discovering it, (ii) to coherently present a number of basic techniques and results, currently used in the subject, to those working in it, and (iii) to present some of the results that are attractive in their own right, and which lend themselves to a presentation not overburdened with technical machinery.