What's the catch? Usually outfits that offer "free, just pay shipping and handling" books keep your credt card info and begin to send you unsolicited, expensive additional material.
I'm going thru Option Market Making by Baird right now. I doesn't seem to be telling me anything new that hasn't been mentioned by Natenberg or Sinclair. Perhaps, I should keep re-reading Sinclair and play with my pseudo models until I totally get it. For now, I'll keep using books as a panacea.