This is a 0 exp card? Really?
The book is pretty much game breaking given the power level of tactic cards. The simplest and most broken usage is replaying First Watch 4 times, which kills the game regardless of the difficulty because, to be fair, more than half of the game challenge comes from randomly drawing encounter cards. With the help of Stick to the Plan, you will only need to find this book in your mulligan to shield your team from unwanted encounters for 4 turns. Not only that, your can add Ever Vigilant to save your team actions of playing assets at the beginning of the game. 4 assets are not enough? Sure, do another rounds to play 8. You'll feel pretty much no blocker in the scenario after all these, unless your team has disastrous deck building or team composition.
What do you need to achieve these? 6 exp for Stick to the Plan, easily achievable after scenario 1 with In the Thick of It and Delve Too Deep; 4 exp for Ever Vigilant, after scenario 2. All you need to do then is drawing 5 at the beginning of the game, no The Book of War? Mulligan all 5!
Carson will be an ideal executor of this as team support, because he can take seeker cards to draw for the book if it does not show up in start hand and recharge it using Truth from Fiction.
Some additional thoughts on tactic cards
We know that guardians are usually restricted by draw power and resource gaining, though a lot of guardian cards are pretty powerful, like they ones I mentioned and those other comments mentioned. Typically guardians have difficulty drawing these cards in a consistent way at the beginning with the game, unless it's a tactic and you have stick to the plan, or even if you do, you need to draw through your entire deck to play those powerful cards again, which is not what most guardians are good at.
Now with this book, that is not a problem. You can put powerful tactic cards under stick to the plan to access them consistently, then search for this book to play those cards every turn, up to 4 times before a reshuffle. This does not seem right to me based on the power level of those tactic cards, because they were designed when guardians can play them only once in each reshuffle.
This card is a guaranteed nerf to me, to 3-4 exp, or even made exceptional or removed from game after you exhaust all secrets (even that will not truly stop it because we can easily recharge it with Enraptured and Truth from Fiction).