Before PR any book, I have tried to state a purpose for the book, for novels, my purpose is simply and little, read for fun, trying to get more possible from experience of reading. For technical book my purpose is used to be learn the content, and integrate the methods, formulas and ways of work in my mind, so later you can use it fast and with trust in not makinkg errors. (I talk about books of maths, physics, programming, ...)
