For a dead product line, I really enjoyed the Explorer Society book. The Roll and Keep is a good system, and I enjoy the 7th Sea storyline. Well, other than the parts involving aliens. Thankfully, the Explorer Society delves into the "atlantean" technologies without bringing aliens into my fantasy.
I'm one of those players (and GMs) who likes to bring as much of the game as I can to life, so when I started using proper Explorer Society lingo in the game, and it caught on, well, that's just more buy in.
If you're playing the Seventh Sea, I greatly encourage you to play a member of The Explorer Society, and this book will help you out a great deal.