As a result, I've set up a Wiki for it on one of my domains, so that as I find out all the things that I want to know (for example, Julian's hair colour is mentioned as black later in Nine Princes in Amber, even though it's only mentioned as "dark" in the trump description) I can put them in a place that's findable later, and that others might be able to use.
So, for your edification and enjoyment, I present the AmberWiki. Currently there's very little there (I think I've done two articles so far, and one of them was almost completely copied from Wikipedia) but as I go I'll be adding more to it as I do the research.