That’s a six book series, if I remember rightly. I love Pratchett’s stuff (Men at Arms is next on my Discworld reread) but I was thinking of his solo stuff. Normally I just start at the first published if I think I’ll enjoy the whole lot.
If you like hard sci-fi, his NASA series is excellent, especially Voyage and Titan. They describe expeditions to Mars and Titan using Apollo era technology, in such a believable fashion that you think it could have really happened.