DeFelice presents this intricate subject in an easy-to-follow, stepwise fashion: he reviews the fundamentals of electricity; transfers those principles to a biological context; and expands the discussion to encompass the subject's practical dimensions. Clear definitions and intuitive descriptions characterize the presentation, which is complemented by over 150 drawings and graphs. Mathematics is kept to the minimum necessary. The text covers both excitable and non-excitable membranes and includes the plasma membrane as well as intracellular membranes. A unique, `electronics-made- simple' appendix, designed specifically for biologists, treats the operational amplifiers used in patch clamp, and other appendices offer solutions to equations and examples that illustrate principles.