Reading a used book is easy, and you already have some reading skills since you're reading this. However, there's a difference between reading and reading well. How you read a book depends on why you're reading it. Individuals who read for entertainment read differently than those reading to learn. When reading a book, read the whole book, not just the story.
Reading the preface, table of contents, any indexes, and the inside of the cover can help you learn about the author and the book to determine whether or not it's something you want to invest time into. For example, many people read novels superficially; they typically read for entertainment and don't need to study the words or ideas on a page. However, you read a textbook much differently than you do a novel. You might have to study the ideas and information in a textbook, which requires more brainpower.