Using 1,5 hours per 3-4 pages is definately to much. My guess is that it will ruin anybody's motivation.
Imagine if your book is 400 pages. Then you will use at least 150 hours to read it which is equal to 20 days if you manage to read 7,5 hours per day.
I can usually do 20+ pages per hour and have complete all my exams with good results. My tricks are:
- Use memory techniques, so I can remember almost everything from the book.
- Apply the subject in real life, so you improve both your understanding and your memory.
Concerning memory techniques I recommend this book:
The Memory Book