Full Metal Panic is based on light novels, yeah. I read them all about ten years ago, machine translated. They're releasing them officially now.
The anime (4 seasons) covers 9 out of 12 volumes. Season 2 doesn't cover any, it's side stories focused on comedy (genuinely hilarious btw, you simply must watch it at some point). Hoping we get season 5 someday.
As for something to watch, Serial Experiments Lain? I've watched a few eps, never finished.