Just went back to check--the annotations telling all the characters in The Bloody Red Baron goes from page 551, through 563, with another two pages worth of acknowledgements. Plus another 18 pages of notes that follow that. I think this is just something he's compelled to do, at this point.

I read a novel of his starring Sebastian Moran from the Holmes stories, and while there aren't as many cameos wandering through as the Dracula books, it's still a lot.