Not only sci-fi but fantasy too.

E. Gary Gygax should also be part of a reference library. I seem to recall him as the authority on mediaeval weapons, an essential part of many worlds. Jane's Fighting Ships (not sure of the title, but you can find it from that) and any companion Jane's books will help with more modern settings.

Discworld is a wonderful example of a thoroughly implausible world that works. There is not a hair out of place.

Alternate Earths are another option. The only example that springs immediately to mind is the Wildcard series, starting with Jokers Wild.

I could write a post on this, but you did it first.

Trust me, I'm a doctor.