Best GURPS supplements in other systems/campaign design?

So I am about to start work on design of a small sci-fi campaign for a space fringe of civilization game. I was looking for some good support material to design the subsector in detail with consistency and somewhat hard basis and was led to GURPS Space and Spaceships. Now I have no intentions of running GURPS (not my players cup of tea at all) but I have heard that people swear by their supplements for use in any system. I know they are usually well researched and even include long bibliographies.

I know most of their historical books are great for reference, but what other books are great for setting or other similar information? Where there are minimal GURPS rules and just good information or design ideas to use for other systems.

For instance, is the fantasy and magic books good for use with other systems as a reference? Obviously pure setting books fit here (speaking of, is Banestorm good? What about other GURPS settings?) but what about the tech books? Are they mostly "here's rules and stats on tech" or more informational?

I just might start working on a collection of reference materials, starting with GURPS supplements.