If you like to go under the hood of Mac OS X, or if you've been forced to by quirky problems, you'll want to check out our latest ebook, freshly revised for Leopard - "Take Control of Permissions in Leopard." Written by Unix guru and Mac aficionado Brian Tanaka, the 87-page ebook mixes practical how-to details and troubleshooting tips with just the right amount of theory as it explains permissions in relation to how you keep your files private, copy files to and from servers effectively, set the Ignore Permissions option for external disks, repair screwy permissions, and delete those files that just won't die.

For those who want to learn advanced concepts, the ebook also delves into topics like the sticky bit, symbolic versus absolute ways to set permissions, and how to work with bit masks. In particular, Brian looks at what's new with permissions in Leopard, including the disappearance of the NetInfo database and the increased use of access control lists. Don't worry if you're not accustomed to using the Unix command line in Terminal, since Brian provides extremely clear instructions for that, along with how to manage permissions from the Finder's Get Info and Inspector windows, and with more-capable third-party utilities.

Those who already own Brian's earlier "Take Control of Permissions in Mac OS X" can upgrade to "Take Control of Permissions in Leopard" for 75 percent off; just click the Check for Updates button in your existing copy to access the discount.