Systemantics/The Systems Bible, by John Gall, for a lighthearted, whimsical introduction through real-world examples across a range of industries. An Introduction to General Systems Thinking, by Gerald Weinberg, for a more rigorous/structured introduction.

I've heard good things about Donella Meadows, but I haven't read anything of hers yet.

If you really want to start learning about systems, go for Incose's setup: https://www.incose.org/

You might find some of their handbooks online free of charge (maybe not the one most up-to-date).

There is a really good book written by Haberfellner called 'Systems Engineering' which to my knowledge is only available in German. The book is awesome though: https://www.amazon.de/Systems-Engineering-Grundlagen-Reinhar...

Oh, it seems like they finally managed to get it translated - apparently available in July this year: https://www.jpc.de/jpcng/books/detail/-/art/reinhard-haberfe...

I did my Master's degree in Systems Engineering based on both Haberfellner and Incose's handbook. It's been great learnings which have been useful ever since helping me to separate all kinds of problems as both a software developer and a systems architect.

So, enough said - separate and conquer ;)

There was a recent Ask HN here[1] asking just that. Some of the suggestions overlap with what others have provided here, but it may be useful.

[1] https://news.ycombinator.com/item?id=19133097

Isn't that a different kind of "Systems Thinking"? This one is about feedback loops.

Hanselmanns is about operating systems stuff.