There have been a couple of good Seaman books published and the Chris Nixon book should be terrific, he's the guy who did "Mon Ami Mate". A few years ago there was a nice article about Richard Seaman in Car magazine, had a pretty ghastly photo of his burning Merc wrapped around a tree at Spa. Looks like his accident happened right about where the pits are located now, on the approach to the La Source hairpin.
Personally I've always been more intrigued by Bernd Rosemeyer, the forerunner of Rindt, Peterson & Gilles Villeneuve.
John