Everytime I want to understand control theory better I stumble over this and the literature is often quite (deliberately?) obtuse.
It can be bought, but is available for free. Code is also available via GitHub. It uses Python and Jupyter.
"The premise of this book (and the other books in the Think X series) is that if you know how to program, you can use that skill to learn other things. I am writing this book because I think the conventional approach to digital signal processing is backward: most books (and the classes that use them) present the material bottom-up, starting with mathematical abstractions like phasors."
https://jackschaedler.github.io/circles-sines-signals/
It's also done with (an old version of) d3.
If it does then I can recommend Practical Signals Theory with MATLAB Applications by Richard J. Tervo
Lots of real world examples of systems and signals in a level appropriate for a first DSP class.
Honestly it's kinda like linear algebra in that everyone has their own favorite and there is a place for many styles. The best thing is to go a nearby college library and look at a lot of them and find an author that speaks to you.
of the standard texts, my favorite was the proakis one.
also used linear systems and signals by lathi in school, it was okay.