This may seen like a weird question, but since we're challenged--as engineers--to constantly adapt to changing technologies, we always find ourselves buried in documentation. That said, we also need to consider that time is of the essence because people want their stuff fixed and improved with little hesitation if any.

How do you get through lengthy manuals, books/manuals within a short period of time?

Take for example: "The Linux Programming Interface," by Michael Kerrisk, which is roughly 1500 pages in length. How would you get through a monster of a book like this if you're pressed for time while still learning most of the material?