Some interesting or high-value Tactic events I came across:

• First Watch: Such a good card. To play it each round is bonkers.

• Counterpunch: This is one of the no-brainers and probably the intended use of the Book. Don't waste precious actions on enemies, just play this.

• Ambush: Before grabbing enemies via "Where's the party?" or Kicking the Hornet's Nest during your turn.

• Dynamite Blast: If you have enough resources, this could be strong.

• Barricade: For sticky situations where you want to get rid of engaged enemies or some effect causes enemies to move during the investigation phase. Basically just to circumvent the forced effect.

• Hiding Spot: Since this card has no play instructions you can play it during ANY player window and your whole group benefits from its effects during the complete investigation phase. Next turn, repeat.

• Hit and Run: I am sure with a bit of theorycrafting you will find sweet combos via recurring this. Dunno, maybe Charlie Kane with Summoned Hound or The Red-Gloved Man? Or tarot plays with Anna Kaslow? Or Library Docent to replace your empty Book (if you have another Tome in your hand).

• In the Shadows: As long as you don't have to kill enemies it's great to be invisible all the time without having to rely on crazy deck-cycling builds. Additionally, Trish Scarborough actually has great access to secret replenishment to get even more out of the Book. Needs Versatile, though.

• On the Lam: My personal favorite. I built a whole deck around playing it each turn and eventually blasting the horde you gathered via "Where's the party?" and Kicking the Hornet's Nest with Dynamite Blast and Stir the Pot

• Additionally, you can combo the Book with Crystallizer of Dreams, which feels wow :)

There is Making Preparations, but Dilemmas are not played, so this doesn't work (also for this card, it wouldn't make sense to recur it).

It's funny that a lot of Tactics let you either avoid enemies or rough them up real good. Then again, it's sort of in the name.

I have re-checked the erratum on Wendy's Amulet but I don't think it prevents the below interaction to work.

In a 2+ game, give it to your main fighter in addition to On the Hunt: during the mythos play On the hunt, spawn the enemy, use The book of war, defeat the enemy, get your resources, and at the end of your turn get On the hunt back.
Replay each time you need an enemy (for Parley effects, Under Surveillance, Ambush, ...)

In a Zoey Samaras deck you can even kill the enemy when you engage it thanks to the Zoey's Cross. Especially interesting for Aloof or Cultist enemies: Acolyte, Whippoorwill, ...

P.S: if this combo doesn't work due to the fact that On the Hunt is not discarded right away, there is the inferior combo with On the Hunt / Kicking the Hornet's Nest (you need to find an enemy among the first 9 cards of the encounter deck.