The next chapter that Harris offers is a wee one, asking whether or not the truth he is offering might be bad for us. He doesn't think so, and offers his own testimony -- how "losing the sense of free will has only improved [his] ethics" (p. 45).
There he goes again, writing as though he lost his sense of free will because he somehow discovered the actual state of affairs out there in the world. He does this after spending numerous pages demonstrating why it is, assuming his view of the world, that nobody has any idea of why they do or choose anything -- including why they might want to assume his view of the world.
Although his view of things is stark, he is willing for us to pad it a little bit.
"Our interests in life are not always served by viewing people and things as collections of atoms -- but this doesn't negate the truth or utility of physics" (p. 46).
Translated into plain English, this means that free will is an illusion, albeit an illusion we ought to permit ourselves to function with a bunch of the time. If we admit that we are ultimately being steered, we can "steer a more intelligent course" throughout our mechanistic little lives.
If we admit that Dad is actually driving the car, our three-year-old selves can sit on his lap and pretend we are the ones turning the wheel.