On: Quantum Leaps, Long Assumed to Be Instantaneous, Take Time

[abecedarius]

It's not easy and you'd need to find problems to work, but http://www.feynmanlectures.caltech.edu is one source some people swear by. Others say it's too hard for a beginner text. I think both have a point, but it's free to see for yourself.

https://www.amazon.com/Thinking-Physics-Understandable-Pract... is not free, but also excellent and gentler.