It only covers AutoCAD through version 2007, but if you're new to the program or just never had the chance to explore it fully, this may be the book for you:
AutoCAD: Professional Tips and Techniques by Lynn Allen and Scott Onstott
Other AutoCAD/LT 2008 books can be useful as well, click HERE.
Want to print your own? Explore these free guides for AutoCAD 2006, AutoCAD 2007 and AutoCAD 2008.