Hi scmetzger,
Somu Shankar, a guy who scored 740 in the GMAT, used the books from 4GMAT especially the math resources. According to him, the 4GMAT math books start from basics and teach lots of short-cuts. It is affordable as well. He told me that he finished the Quant section with 15 min. to spare.
I don't have any personal experience on them but 4GMAT books seemed to have worked for Somu.
You can check this site and compare it with other prep books like Kaplan, Manhattan, Veritas, etc.
https://www.4gmat.com/prep_courses/math_ ... rial.shtml
Best regards,
Gabriel
Do the very best that you can and God will do the rest
