I really enjoyed them, but I wouldn’t say there’s any replayablility there. I enjoy the dark atmosphere and a lot of the fun for me was just the discovery and seeing what sort of creepy stuff coming next. Once the games were finished I didn’t feel the urge to play them again.
When I was a kid my parents bought me a book called “practical astronomy with your calculator” that went over all the workings and formulae for calculating eclipses, moon phases, locations of the planets and heaps more. If you want to get into it I highly recommend this book or something similar.