The books are available in PDF form. The most germane would be the core rule book, Shadowrun, 20th Anniversary (which is a mild revision of 4th edition). If you want to keep expenses contained, look for a cheap 4th ed. book. I've been working on a rule summary / index that might condense the rules to a couple pages, which I will post ASAP along with the Pre-Gens. I will have the summary available at the Con so that I and all the players can use it to make us all more competent and efficient.