Following @cornsnicker3's lead...here is what worked for me and some thoughts for future test-takers. This was my first (and only) time taking the exam.
The only books I ended up using or needing were MERM, Engineering Unit Conversions, and steam tables. The steam tables I used were a version published by Iowa State University which I held on to from my undergrad. I actually looked into whether they still print them, but couldn't get an answer. They were a huge help though as they were much more comprehensive than anything else I found. I did not have to interpolate a single time to get through the exam. If you are questioning the need for the Engineering Unit Conversions book, GET IT! I used it a lot while studying as well as during the actual exam.
In general, my studying looked like this:
Started by attempting to read through MERM in its entirety and gave up after 3 or 4 chapters.
Completed the NCEES 2016 practice exam twice un-timed. On the second pass, I made a note sheet of all the commonly used equations. This eventually became my exam "cheat sheet". Completed the exam a third time (not in one sitting) timed. Also tabbed MERM as I went along.
Completed Slay the PE once un-timed. Made additions to my cheat sheet as I went through. Made sure I understood each problem.
Completed Slay the PE (not in one sitting) timed.
WEEKEND BEFORE THE EXAM: Completed NCEES 2016 in one sitting (giving myself the same format as exam day with a one hour break between AM and PM sessions...also did not allow myself any scratch paper besides the exam itself). I made a point of not even looking at this exam for about 6 weeks prior to this so I would hopefully not just remember how I worked out the problems. I also went through and worked out all of the practice problems that @Slay the P.E. posted on this forum.
Not sure total number of hours studied, but would guess somewhere in the 100-150 hr range.
Opinions on practice exams taken:
NCEES 2016 - Spot on as far as difficulty and type of questions.
Slay the PE - Definitely more difficult than the actual exam, but really helpful as it hit the right topics. Definitely worth the investment for the solutions.