Yeah, I used to get these kinds of triggers. Basically a trigger is us taking up the mantle for the original abuse. So, my mom used to say to me all the time when I was a kid "Oh you'll never finish, you never finish anything" So every time I'd start a book - even novels - I'd feel like I had to barrell through. And I took up the mantle and did it even better, not only did I have to finish the book but I had to read it from cover to cover, including the introduction, and finish every exercise and if I didn't an indictment was sitting there looking at my from my bedside table every night and every morning.
Yes, you can get triggered and you don't have to read it now, or at all, you can do what you want to do, what you need to do. And he does say to go to the chapter you need. Skip around if you need to or use one paragraph and not even a whole chapter. Recovery takes time and yes effort and it happens in non-linear ways. Give yourself a big gigantic break. Pat yourself on the back for every single thing in the right direction - you deserve it, you need it, you need to have validation for even the tiniest step, and you need to do it. Because aside from a really good therapist no one is going to take care of us. We were set up to NOT be taken care of by the narcissist, by the abuse itself, and at the same time set up to expect that someone else should. But it is not going to happen. Part of self care is thanking your self for taking care of your self. Putting a book down that triggers you, or flipping to the chapter you want to work on IS self care.
You will find what you need to heal so long as you keep looking. So keep looking.