An October candidate recently reached out out to me privately on this forum asking this question so I thought I would share it with the masses as well.
I took this exam in California (San Mateo) and I am an Ohio Resident so that meant air travel and space considerations. That's important because the number of references, for me, was limited as I was not willing to chance them travelling in a checked bag.
First, a little background: I started as an industrial electrician in 2006. I pursued my engineering degree part time starting in 2008. I earned my AS in 2012 and BS in 2015. I began working in the engineering space in 2011 at a consulting firm, then moved on to a large OEM then finally found myself at a power engineering and services company.
This exam is not easy but it doesn't have to be brutal if you can properly prepare yourself. Take it seriously and you'll be fine.
My study schedule was more haphazard than most. I have 2 kids (8yo and 2yo) and an otherwise active lifestyle so finding the time meant just grabbing what free hours were available, when they were available. Basically, I studied for 1-2 hours a night (no less than every other night) for the 4 months leading up to the exam. 1 month out, I set aside 4 hours on a Saturday and 4 hours on a Sunday and did the NCEES practice test in two parts to assess my status. From there I focused my efforts on problem areas. All in, I believe I had some 200-250 hours if I include some pre-studying before the 4 month mark.
My primary resource was Engineering Pro Guides. I used the Technical Study Guide as the guiding document and supplemented with other resources. I used all of the following throughout studying but they are listed in order of importance relative to exam day:
ENG Pro Guide Technical Study Guide -- https://www.engproguides.com/power-pe-exam-study-guide-tools.html
Get all of his practice tests. They are very, very good.
The Electrical Engineer's Guide to Passing the Power PE Exam by Graffeo -- http://www.powerpeexamguide.com/
National Electric Code, non-handbook (I was an electrician before so I didn't need the extra weight of the handbook) -- https://www.barnesandnoble.com/w/national-electrical-code-2017-edition-nfpa/1123827199#/
I'd get the tabs for this no matter your level of familiarity
Electrical Machines, Drives and Power Systems by Wildi -- https://www.amazon.com/Electrical-Machines-Drives-Power-Systems/dp/0131776916
Power System Analysis by Grainger -- https://www.barnesandnoble.com/w/power-system-analysis-john-j-grainger/1100151989
I didn't use this one much on the exam but there are some odd ball items in here that can be helpful
National Electric Safety Code -- https://catalog.nfpa.org/National-Electrical-Safety-Code-2017-Edition-P17436.aspx
Try to borrow this one if you can as its expensive but there are not likely to be a lot of questions needing it. Easy points if you have the book though.
Various printouts bound in 3-ring binders for topics I struggled with but weren't well covered in the above. For example, battery calculations, certain power electronics, certain equipment standards, etc.
Like I mentioned above, I was an electrician before I got into engineering so my base code knowledge was above average. That said, ENG Pro Guides has an excellent practice test. Find your way through that a couple of times and you should be fine. The key is to learn how to use the index and recognize key words, not memorizing the whole book, which is impossible.
Hope this helps. Feel free to ask anything else and I'll do my best to answer.
Thanks and good luck!