The book is decent - better than a few I have purchased but suffers from a common failing in technical books - it is repleat with errors. Really, a book which is used by some in technical schools or colleges should have only a few errors at most. This book has scores of errors, which makes learning very difficult. Like most subjects if you intend to teach yourself, you will need three or four references including PLC manuals in order to resolve the many ambiguous diagrams and statements in the text...