I know people who read and read, and for all the good it does them they might just as well cut bread-and-butter. They take to reading as better men take to drink. They fly through the shires of literature on a motor-car, their sole object being motion. They will tell you how many books they have read in a year.
Unless you give at least forty-five minutes to careful, fatiguing reflection (it is an awful bore at first) upon what you are reading, your ninety minutes of a night are chiefly wasted. This means that your pace will be slow.
— Arnold Bennett, How to Live on Twenty-Four Hours a Day
My own reading is quite slow because of all the pregnant pauses, but this quote is a great reminder that I need to mull more. I would also recommend Henry Hazlitt's Thinking as a Science, which is where I discovered Bennett's book.