I believe that there is an error in the Mac OS X Leopard edition , with regard to sharing iTunes between multiple user accounts on one computer. The "Gem in the Rough" box on page 444 indicates that by moving the library to the shared folder you can access it from another account on the same computer. When I did this, I could see the files in the second account, but iTunes could not access them. Incidentally, a Mac Genius at a Mac store gave me this guidance as well.
When these steps didn't work, I called Apple Care and they told me it wasn't possible at all. I was able to make it work by going back to the original iTunes account and enabling sharing. After that, the full library became available in both accounts.
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Thanks for letting us know about this issue, and for sharing your solution. A similar note has been submitted as errata for the book (you can view/submit errors for any of our books by following the link from the book's catalog page.).
The issue is still unconfirmed, but if confirmed by the author or editor, this will be noted on the book's confirmed errors page, and then will be corrected in the next printing.
I'm glad you were able to figure out a solution. Let us know if you encounter any other issues with this book (or submit them here).