I ask the question here few months ago, do you really need to study from the books, the answer I got was yes. I do not consider Graffeo guide, Pro Eng Guide notes as books. They are notes. Books to me are Grainger, Wildi, Camaro etc. You don't really need to study from books provided you are an electrical engineer and have been working in the field for past several years, so you are not going to be brand new to concepts such as PLC, drives, CT/PT, grounding etc
You need to be strong in certain areas for e.g. Math, Circuits and other things.
Since I did PE right after FE everything was fresh and my experience may be different than others. I'm not recommending anyone not study from books, just stating my experience, although I did skim through the books. I did not retain much from the books. Solve a lots of problems.
Know one thing that many people go through similar cycles, in a month of studying they automatically figure out what is important, what to study how to study. what to study from books? The important thing is to start with familiar topics and build.
Heck I even didn't know how to tab, what to tab? I was afraid that I won't even have a binder full of pages when I saw previous test takers had 2-3 full binders. By the exam time, even I had enough papers for 2-3 binders and I had to cut back. I just didn't know what to put it in my personal binder and what was I going to fill up with. That is why it is important to start at least 3-4 months/5 months preferable before the exam, so even if you are not efficient the first few weeks, you can still make it up.