Here are some suggestions:
Don't look straight ahead, look at a point on the floor about 6 feet in front of you.
GET SHOES.
Sit back more and get a piece of wood to put in front of your foot. If your knee knocks it over, they it is travelling too far forward.
Try widening your stance a little bit to ensure knees don't go too far forward. Shove the knees out hard.
Your bar path is far forward of your mid-foot or heel. It makes squatting harder when the bar isn't in line with what is pushing against the ground (e.g. the heel).
Did you read the book?