I have read Discworld both by series (Wizards, Witches, The Watch, ..) and in order, the good thing with reading in order is that you get a break from the different characters and you notice the cameos easier.
I have been following John Scalzi on Twitter (and now mastadon) for many years, but I still haven't read anything from him. I think it's about time I do something about it.
I was going to start on Ian M Banks' Culture series, but I read a few reviews that said his writing style is a bit repetitive, and then I found John Scalzi, my first impression of Old Man's War reminds me a bit of Pratchett and Douglas Adams, and I hope it continues in that fashion.