UX is a huge field with a lot of entry points so it’s difficult so suggest a single resource to start with.
However I’d suggest that coming from an engineering background, you might find joy in learning about user testing first as that’s usually a big eye-opener that helps you understand why the field of UX design is important.
A classic book to start with is “Don’t Make Me Think” by Steve Krug[0], which covers usability testing and even how to conduct a session yourself.
Then there’s “The Design of Everyday Things” by Don Norman[1], whom many consider the ‘father’ of the modern field of UX. That one can be a bit dense though.
If you want to think like a designer, then learning about Design Thinking[2] is a good place to start.
Hope that helps!
[0] https://www.amazon.com/Dont-Make-Think-Revisited-Usability/d...
[1] https://www.amazon.com/Design-Everyday-Things-Revised-Expand...
[2] https://www.ideou.com/pages/design-thinking
