KL90
So I took the GMAT for the first time today and did horrible. I was hoping for north of 600 and got 530. I'm pretty devastated, as I felt my preparation was fairly good. So I plan to rewrite, however I return to my job in two weeks where I work 70+ hour weeks and only have one day a week off (this day is generally devoted to running errands, grocery shopping, laundry, etc.). So my question is, what would be an good study approach for me with my time constraints? I did fine on the verbal and am not too concerned with my score there but it is definitely quant where I need to focus. Any good books that anyone could recommend? I am hoping to rewrite in late Jan/early Feb - is this too soon given my time constraints? Any advice would be appreciated, I'm feeling pretty lousy today

Welcome to GMAT Club!
Sounds like a tough proposition with that work schedule.
My recommendation would be to study BEFORE work. Wake up at an early time and study then. That may sound painful but it depends on your commitment level. I can tell you it will be a better result than doing it after or during work. I would recommend 1-2 hours in the morning of study time that should begin with review of yesterday's material and review of questions you did not get right to make sure you can solve them today.
The books I would recommend would probably be:
#1 Foundations of GMAT Math by
MGMAT #2 Kaplan Math Workbook
I doubt that you have enough time to do anything more detailed such as the
MGMAT guides or Veritas Prep Guides.
P.S. Did you know that 530 is 50th percentnile on the GMAT? About average...
P.P.S. Also see this thread:
how-to-improve-your-quant-from-q30-to-q40-142810.html