There is a general web page set up with information on OpenLDAP which is the version of LDAP we're using (are there others?) The web address is http://www.openldap.org/. One of the links on this page is to the FAQ-O-Matic, where one of the FAQs is ``Where can I get more information on LDAP?'' I downloaded the free book published by IBM called ``Understanding LDAP'':
http://www.redbooks.ibm.com/pubs/pdfs/redbooks/sg244986.pdf.This book thoroughly explains the concepts involved behind LDAP. It is quite basic (the level is a bit too basic) -- but I prefer such a book to one for which the level is not basic enough.