I apologize if this the wrong forum, but I highly recommend MGMAT Foundations of GMAT Math
for anyone struggling with quant. By no means am I ready to sit for the GMAT, but my score jumped from 350 (20Q,19V) to 550 (37Q,29V) just from completing this book.. The book is massive! It took me about three months with work to get through it, but it's worth it.
I just started a Veritas Prep
course Monday, and I am hoping that by the end I can increase another 150+. Good luck everyone!
Long journey, but not impossible.