In order to separate the mission from the payload, my answers:

1) I think I'd rather do fiction and non-fiction. "sci-fi related" ended up kind of open-ended.

2) I've been doing both clubs, and will likely continue to do so.

3) I'd really rather read something new, but I've also just finished two really, really good books, both of which are likely to be provocative and enjoyable to a vast swath of people here. Not only that, but they both kinda blend the lines.

My "non-fiction" suggestion would be Our Mathematical Universe by Max Tegmark. This is a book on Life, The Universe and Everything that starts with mainstream cosmology and ventures forth into pretty crazy multiverse/philosophy territory. It reads kind of how Feynman would read if he were to write his first book two weeks ago, rather than his last book twenty years ago. Considering how much string theory and quantum suicide gets bandied about around here, it might be an interesting read. And it's pretty quick.

My "fiction" suggestion would be The Martian, which is basically "Castaway" or "Apollo 13" if Tom Hanks were Louis CK and instead of an island, it was an aborted Mars mission. There's a shit ton of geeky math stuff in here that passes my sniff test but also makes me willfully suspend disbelief enough that I didn't breathe in very hard.

The disadvantage of both books is I've read them, but I recommend them both wholeheartedly.