Thank you for your input. The Object API AddressBookEntries object also has a count property you can read, but it only provides an estimate if you are reading the system address book. Here’s an extract from the documentation on Novell’s site:
The system address book does not keep an actual count of the number of users in the book. The count that is returned is an approximate count that is based on an index count. Since the index is not updated with every delete (for performance reasons), items that have been deleted will still be included in the count until the index is rebuilt. If you want an exact count, use the AddressBook object to iterate through every entry in the book and count each iteration.
You can find the complete documentation here.
I hope this helps.