Unfortunately there is no good book I have come across about the philosophy of Whitehead since the Living Philosophers series in the sense of quick and direct and succinct. Whitehead has developed his own lingo and rightly so. "Process and Reality" is supposedly his philosophy masterwork and one of the best of the best, right up there with Heidegger's "Being and Time," but was written while he was still a mathematician and in transition. However, he develops ontological categories there that Aristotle wouldn't have dreamed of on his best day. Won't be any shortcuts here.
Ah, so there's no royal road to philosophy, either, eh?
Thanks for the tip, will look it up.
Cheers!