Good computer books are worth their weight in gold, because the online help in most applications leaves a lot to be desired. Unfortunately, while millions are spent programming software, considerably less money is allocated to documenting it. Worse yet, the documentation is usually last minute, rushed and never read by anyone but the unfortunate user. Having auxiliary documentation in the form of books is extremely helpful.
How to find a good book is simple. Get two or three on the same subject. Today, software applications are often the culmination of decades worth of functions and features that includes everything everyone ever wanted in the program. It is rare to find a single author equally competent in all areas of the program, and you will not know that when you browse the book in the bookstore, only when you have a question later on. If you have more than one book, your chances are greater that your question will be answered.
In lieu of direct technical support from the software vendor or from your organization's help desk or IT department, several books on the subject is often very helpful. See tech support