It is well known that magnetism is a relativistic effect. The combination of Coulomb's law of electrostatics and Einstein's special theory of relativity demands the existence of magnetic forces and hence magnetic fields. However, although many books have drawn attention to this fact very few have attempted to use it as the basis of a unified treatment of electricity, relativity and magnetism, and none, as far as I am aware, have extended that treatment to include the quantum theory of magnetism. Derek Craik's new book does all of the things, and does them with considerable thoroughness and a good degree of clarity. For these reasons it will be a valuable addition to many college and university libraries and will be of interest to all those involved in the teaching of electricity and magnetism at tertiary level.

Electricity, Relativity and Magnetism: a unified text is divided into four substantial chapters. The first, and shortest, is devoted to special relativity. In just 35 pages it covers the essentials of the subject, including length contraction, time dilation and the transformation laws of velocity, acceleration and force. The other three chapters deal respectively with electromagnetism, magnetic behaviour and design (including practical field calculations and the energetics of domain structure) and the quantum theory of magnetism. Each of these latter chapters is about a hundred pages long, and therefore in some danger of becoming indigestible, but all of the chapters are subdivided into manageable sections and subsections that are usually just a few pages in length. The sections are well focused, but unusually wordy for such a mathematical text. Indeed, wordiness is one of the hallmarks of this text. The author is seriously concerned to present a specific approach to his subject, not merely a catalogue of results. This is refreshing and worthwhile, but it does mean that even in the second chapter, which deals with such familiar topics as dipoles, polarization, Maxwell's equations and electromagnetic radiation, the reader will have to pay close attention to the text in order to fully appreciate Craik's particular approach.

The author's concern to adopt an individual approach to his subject is evident throughout this book, but his deep familiarity with the material really becomes apparent in the third chapter. It is here, amidst notes on numerical techniques for field calculation, comparisons of SQUIDs and conventional magnetometers, and discussions of magnetic behaviour at high frequency, that one really feels in contact with modern magnetism. It is telling that the list of references at the end of this chapter runs to more than 30 books and papers (including one of the author's own papers), whereas the relativity chapter ended with just two references, one of which was to Einstein's 1905 paper.

Craik's discussion of the quantum aspects of magnetism is not unusual in itself; such standard topics as spin-orbit coupling, exchange integrals, crystal field effects and spin waves are all included, but it is unusually self-contained for such a relatively brief treatment. It starts with a 15 page survey of non-relativistic quantum mechanics, and follows this with a similarly concise survey of Dirac's relativistic electron theory, leading to an approximate wave equation for the electron in an electromagnetic field that includes spin in a natural way. These surveys should have the effect of making the book more than usually accessible, but their density means that those trying to use them for this purpose must be well motivated and perhaps even doggedly determined. It is for this reason that I regard the book as one for the library and for the professional, rather than one for the student.