[thenavarro]

I'd recommend Charles Hamilton's books. He's an entertaining writer. I think a lot of his stories need to be taken with a grain of salt but I like his books. You can google them. I also enjoyed From The President's Pen by Vrzalik (sp) and Minor. From the White House Inkwell (don't remember the author, just google it), is another one I liked.

For JFK, try Hamilton's The Robot that Helped Make a President, and Andreas Wiemer put together a nice booklet of JFK exemplars.

Also, for exemplars, rrauction.com has a nice online database of past auctions with images. You will occasionally find a dud in their database but I've yet to find a dealer that hasn't offered an occasional dud in my opinion.