Print Books are legal when the hardcopy version hits street date.
PDF only products, such as the eBook line, are mostly legal 30 days after they are released. Any optional rules in said books are NOT legal unless otherwise stated in an updated FAQ. The main reason for the delay is both to give us a chance to catch something that is obviously broken and fix it (Either through eBook eratta, or with an FAQ update) and to give the product a chance to be picked up by the masses, since a lareg portion of Shadowrun players don't check out the website, forums, or facebook page on a daily basis and snap up new PDFs the moment they're released (shocking, I know!
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Bull