Alright ladies and gentlemen, this one is a bitch. It's not as bad as the engineering book, but it's pretty brutal. There are a ton of rumors swirling around this one as well, just like engineering, and the requirements aren't fully known.
You get this book after you finish a questline involving Christine De Pizan. There are 4 missions, 3 fetch missions and then a standard mission where you just take a base. The problem being, only one event can happen each time you enter the tavern, so it can be very hard to get side quest events like this one to show up if you always advance the story.
After you get 3 star fame, you should eventually be visited by Christine De Pizan in the tavern. Talk to her, and she insults everyone and that's that. Eventually, the fetch missions will start showing up in the contract list in the tavern. They have a ! by them but there is no notification from the barkeep or anything that they are on the list, so make sure you keep an eye out for them. The missions are simple, you just run around to different spots looking for stuff she needs. After those three are done, she will visit you once again in the tavern, and then another ! battle will appear. In this one, you simply need to take the base.
I've read around that if you wait too long (like post-game for example) you can glitch yourself out of getting this achievement, so I decided to do it as early as possible. This is how it worked for me :
-Got three star fame
-Christine showed up a couple battles after I was 3 star
-Got all the way up to the battle of Orleans, the ! that advances you to 4 star fame, but did NOT do this mission.
-Kept doing the missions that popped up. The missions are random, so you'll be getting a lot of events that pertain to other sidequests. I probably did around 50 contracts before I got her third fetch quest to show up.
-Eventually I didn't get anymore events and the fourth quest didn't show up, so I got frustrated and finished the battle of Orleans for 4 star fame.
-After about 10-20 battles in 4 star fame she showed up in the tavern, and I finished the mission.
-I did 1-2 more battles and she showed back up in the tavern with my reward (the tome of explosives)
I suggest doing this in 3 star fame so you don't glitch yourself out of it. Remember, it's all random, so it can take a lot of time. There's a ton of events that can happen in the tavern (probably upwards of 100) and the order you get them in is incredibly random. Patience is a virtue when you are trying to 100% this game.HaloStorm12
provided some info that should help : "if you fail one of the fetch quests you can still get the achievement as i failed the fetch wood one and still got it, also instead of doing the missions you can just pick one before deploying retreat, rinse and repeat until she shows up."
However, do note that a lot of special events pertain to achievements, so don't skip battles related to side events! Only use the retreat method when you just have regular contracts to choose from.