Beautifully written book, a model of clarity and succinctness, equivalent to K&R's C Programming Language book, but surprisingly readable from front to back too. I've been working with Unix and Linux since both became available in the UK and I think they're both beautiful from an engineering viewpoint, but often they're not well explained from a systems programming perspective. This book - along with W. Richard Stevens' book, "Advanced Programming in The Unix Environment" - are the best available on the subject in my humble view. I particularly like Kerrisk's because he obviously thought long and hard about the best way to present the material in a narrative format in the opening part of the book where he walks through key concepts, but then he shows the same consideration in each subsequent chapter where he does more of a deep-dive into each kernel subsystem, meaning that it's a book that readers can return to again and again when they want to explore a topic in more depth. It's also a very comprehensive programmer's guide - the coverage is excellent, and the material is bang up-to-date.