The Take Control Of e-book guides are on sale through the end of the year, Dec. 31, at the company’s Web site. These are well-written, easily-search guides to all level of Mac use, including some aspects of Apple computing that a business operator can benefit from.

We’ve reviewed the guide for securing WiFi, for example, and invested in our own copies of the Snow Leopard guides (Upgrading, Exploring and Customizing the newest OS version), the AirPort networking guide (essential if you set up an office net without yards and yards and cables) and even something as complicated and powerful as permissions.

From that last guide I got a tip on FileExaminer, a dandy $10 utility that sets permissions on files so you can transfer music and photos from one system to another without the vexing “permissions not sufficient” error box.

Take Control guides are written by the staff of TidBits, one of the very best Mac resources online. Tonya and Adam Engst have run the company for years as man and wife, a combination that delivers a broader range of strategies.

The guides, delivered as PDF files, cost as little as $5 in the current 50 percent off sale. It’s hard to find a better value for training.