i will suggest u try "the book shop " in vile parle . the shop keeps second hand editions of most GRE books so u can try for GMAT books there i guess .
I stay in Mumbai n I have tried online to get a second hand "The official Gmat Review 10th Edition"....but alas. So i visited some book stores...but they do not have them.
Can anyone tell which bookstores they are available in mumbai...I stay in Borivli...so ne bookstores nearby????