Kjartan Pact of Negation is a key card. You're right that it rarely prevents the Book from being countered, but that's a job for Orim's Chant and Silence. The reason Pact is important is because activating Book on turn 4 usually means tapping out, so Pact keeps the creature land from dying to a bolt when the Book activation is on the stack. And once the lock is in place, Pact can be put on a scepter to protect from spell-based threats. That doesn't protect from everything, but between Pact, Surge, and Orim's Chant, you are protected from almost every threat in the format.

Angel's Grace is a good suggestion, and I used to run it before Orim's Chant. The interaction with Pact was useful, and that is a loss. But Angel's Grace is made worse by being put on a scepter. It essentially loses split-second, so any opponent that can do instant-speed damage can get around it pretty easily. Orim's Chant essentially does the same job, but better. It keeps your life total high, so you don't die to a bolt while your scepter activation is on the stack.

That said, Angel's Grace does do well against some decks, and it definitely deserves a spot in the sideboard.