ian Book has a very high football IQ, that he understands pass coverages, pass protection audibles, and can make adjustments on the fly. Now that he's been able to get in rhythm with the 1st team players, I think he can maintain this level of play.
As far as being the optimal fit, he's about as good as we've had in the past, when you factor in the total package.
His mobility is decent, and his short / medium range accuracy is quite good. I honestly don't know what his long range arm strength is, but with all of the above, it's enough to make this hybrid spread / pro-style offense work at an optimum level.
He's done it against a pretty good defense (Stanford), and the team seems to be in excellent synchronicity with him.