You can park in University Book Store's lot and walk on over, no problem. However, there is another author at the bookstore at the same time, so there's a chance parking might be tight. I've included a map below to help you. The red "A" is the church, and you can see where University Book Store is labeled near it. I'm told there's a public lot near 45th and 15th. You can also see a "P" near the Burke Museum. I'm told there's a lot called N1 in that area that costs $5 after 5pm. When you turn into campus and go through the gatehouse, make sure to request N1. There's also street parking in the area.
If in doubt, just show up early and take the bookstore's lot from the other signing. But you didn't hear that from me. :)
Looking forward to seeing you! And if you can't make tonight's Seattle event, check out my schedule because I'll be signing at Third Place Books in Lake Forest Park next week. The schedule also shows my Los Angeles and San Diego info this week. Even though I'm promoting Gameboard of the Gods, I'm very happy to sign and talk about all of my other books too. See you soon!