Not really keyboard/mouse material but I recently picked up some manuals with instructions for games on the defunct Compuserve online service. When I was a kid I could never afford to be online ($6 hr 300 baud, $12 1200 baud) but I did get a brief taste of it and enjoyed the CB simulator (precursor to IRC?)
Anyhow I'd been looking for manuals for the original MegaWars games and this is the only one I've seen in the past few years. It covers not only those but ALL of the games. No, I can't play them now but I can't help but enjoying reading about them.