I didn't study at all, even though I bought that book. I took it during the last semester of my undergrad work. I took the discipline-specific (ChemE) afternoon test.
My school offered a half day, practice FE exam. One of my friends and I took the practice test, it was basically half the FE exam. They had 60 questions for the "morning" and 30 questions of the general "afternoon" exam (it was half the questions for each session). The morning questions weren't too bad, but I had never had a statics/dynamics class (we only have to take either circuits or statics/dynamics), so I was guessing on those.
The "general" afternoon questions were really hard. I'd say I was guessing on 1/3 of the questions, no matter what the subject. That cemented the decision in my mind to take the discipline-specific test.
I made the right choice, I think I did really well on the afternoon test.
I passed, I don't remember what my score was.
The way they do the afternoon test is everyone gets the same book with all the tests, you just fill in bubbles for your appropriate test. So you could check the questions on each test and see which one you want to take. If you're a mechanical engineering major, you might be OK taking the general test in the afternoon - it seemed to me that the test really was heavy on the mechanical engineering courses.