This is an extraordinarily well written book. In the preface the author promises to prepare system administrators or software developers for building a directory using OpenLDAP using a practical approach, discussing theory where that helps answer practical questions.
Along with some of the best illustrations of the theory and practice of LDAP directory management, this book contains a wealth of detailed information on the servers, clients and utilities that make up the OpenLDAP suite of software. The examples provided of different configurations are not only detailed, they also methodically build upon each other in a way that really illuminates various concepts far better than I think has been done before.
The appendices in this volume are also worthy of mention: "Building OpenLDAP from Source", "LDAP URLs", and "Useful LDAP Commands" -- the last deftly handling one of my favorite pastimes, "Rebuilding a Database (BDB, HDB)".
This book would be an excellent textbook for use by students learning Internet technologies. It would also make a terrific technical manual for system administrators or developers involved in deploying or maintaining systems and applications that use directory services. Finally, it's the one essential book that all directory administrators should have on their own personal bookshelf.