I was in the second year of my PhD when I realized this, and it changed my life forever: that journal articles and non-fiction books are not supposed to be read from start to finish. Instead, always skim through them.
As for how to skim, Mortimer Alder, the author of the book "How to Read a Book" (a book that spent more than a year on the top of bestseller lists), says that pretend to be a detective who is looking for answers to the following three questions:
What’s the big idea?
How does the author make the case for the big idea?
How does knowing this help me?