On time and timing
First, because human attention fades after about an hour, you’ll get more out of three one- hour readings than you could ever get out of one three-hour reading. But be careful: to get one full hour of effective reading, you need to set aside at least one hour and fifteen minutes, since distraction is inevitable at the beginning (settling in) and end (re-arousal for your next task) of any reading period.
Second, make a realistic plan that includes how much time you will devote to each of the three stages. For a 250-page book, I might spend 15 minutes on overview, 4 hours on detailed reading, and 20-30 minutes making notes — but I'd adjust these periods up or down depending on how difficult the text is, how important it is to me, and how much time I have.
Focus on the parts with high information content
Non-fiction books very often have an “hourglass” structure that is repeated at several levels of organization. More general (broader) information is typically presented at the beginnings and ends of:
• the book or article as a whole (abstract, introduction, conclusion) • each chapter
• each section within a chapter
• each paragraph
More specific (narrower) information (supporting evidence, details, etc.) then appears in the middle of the hourglass.