Sadly, Constellation closed a few months back but the con organizers assure me the replacement retailer has all the ISBNs for the authors' current works and should arrive well stocked. Just about every author comes with books of their own to sell in addition to related items (for example, Peter David brings comic book scripts). The Crazy 8 Press authors will be on hand with several titles debuting, as well.
Personally, my policy is not to compete with the bookseller and I only bring out-of-print titles for people to buy since there's always someone who hasn't read our older works. Those and my C8 titles.
The authors in attendance will happily sign anything you stick in front of them regardless of how you obtained it.