"JNDI API Tutorial and Reference: Building Directory-Enabled Java Applications" (Addison-Wesley; ISBN 0-201-70502-8) by Rosanna Lee and Scott Seligman is the first book I know of that focuses just on JNDI. Last year, I read a book on Java and Directory Services, but it focuses on a Netscape API instead of JNDI.

Right after I read that book, I had to debug a JNDI application. Though I was successful, it was painful because I didn't have a book, much less a good one, to reference.

The book follows a format of that the first half is the tutorial and the second half is the reference. The tutorial has 6 sections with a total of 33 short lessons.

The tutorial starts slowly with concepts. Then it builds into programming examples. Finally, it ends with advanced material. The tutorial is very similar in nature to the other tutorials that Addison-Wesley has published in this series. I like the other tutorials and can say the same for this one. The reference is the usual description of classes that you often find in these kinds of books.

I would recommend this book for anyone learning how to program JNDI applications.