This book is a comprehensive account of the theory and applications of regular variation. It is concerned with the asymptotic behaviour of a real function of a real variable x which is 'close' to a power of x. Such functions are much more than a convenient extension of powers. In many limit theorems regular variation is intrinsic to the result, and exactly characterises the limit behaviour. The book emphasises such characterisations, and gives a comprehensive treatment of those applications where regular variation plays an essential (rather then merely convenient) role. The authors rigorously develop the basic ideas of Karamata theory and de Haan theory including many new results and 'second-order' theorems. They go on to discuss the role of regular variation in Abelian, Tauberian, and Mercerian theorems. These results are then applied in analytic number theory, complex analysis, and probability, with the aim above all of setting the theory in context. A widely scattered literature is thus brought together in a unified approach. With several appendices and a comprehensive list of references, analysts, number theorists, and probabilists will find this an invaluable and complete account of regular variation. It will provide a rigorous and authoritative introduction to the subject for research students in these fields.

‘The book is beautifully written with an attractive style of presenting main results then discussing variants immediately in a smaller typeface. The exposition is precise and succinct, yet enough detail is provided for main proofs to be verified. Thus the book will appeal to the student as much as to the specialist. With the importance of the subject to classical analysis as well as to the various fields of application, it seems destined to become a classic. Students in need of inspiration for problems will find plenty here as well.’

Source: Mathematical Reviews

‘The authors presented themselves with an enormous task in gathering material from widely scattered areas to illustrate a single theme. It is a measure of how well they have succeeded that everything now seems coherent and interwoven. For this they deserve our sincere thanks.’

Source: Bulletin of the London Mathematical Society

‘An opera of real analysis …’

Source: Bulletin of the American Mathematical Society