Now rather dated, this excellent little book explores the versatile IC 555; how it works, what can be done with it and, importantly, what its limitations are. That's the good. The bad is that the book is now in the 19th reprint of the 3rd revise and a number of typos seem to have crept in e.g. "I"s substituted for "1"s and "O"s substituted for "0"s which can hinder one's understanding if not aware. Additionally, many circuit diagrams seem have migrated from their associated text into adjoining sections (presumably to save paper!). This is all rather irritating to the reader and detracts from the otherwise useful content. Still, a useful little book and my copy, with pencil corrections and annotations, is on my electronics "Reference" shelf.