"The Design and Implementation of the 4.3BSD Unix Operating System", by Samuel J. Leffler, Marshall Kirk McKusick, Michael J. Karels, and John S. Quarterman (Addison-Wesley Publishers, 1989, ISBN 0-201-06196-1). The standard reference book on the internals of BSD Unix. So called because the cover has a picture depicting a little devil (a visual play on daemon) in sneakers, holding a pitchfork (referring to one of the characteristic features of Unix, the "fork(2)" system call).