Quickly Checking a BookA good way to get the "feel" of a book is to read the table of contents, then read the index, if it has one, and finally read the first and last paragraphs of each chapter.
Looking Over a Computer ManualIf a manual's table of contents lists names of programs or components instead of tasks, the manual isn't "user friendly."
Size MattersBigger isn't necessarily better. If you feel intimidated by the size of a book, you'll probably not read it. Start with smaller, more basic books to become familiar with a concept. Later, you can learn the nitty-gritty details and more technical aspects found in larger, more comprehensive manuals.
Inspiration vs. EducationA book that is predominately pictures isn't bad, but if it doesn't explain what you're seeing in the photos and how to duplicate the look then the book is more for inspiration (such as showcase of brochure designs) than for educating you on how to create the types of items shown in the photos. There's nothing wrong with using books like these for inspiration if that's what you're looking for.
Also see Simple Guidelines That Work Most of the Time for printing, software, business, and more.