Answered a similar question in a different thread: is combine a replacement for RxSwift?
What I recommend is to do not get married with one framework, all frameworks are different with pros & cons and you should make the correct choice based on your needs
IMHO If your development is more balanced to:
- UIKit: RxSwift: Reactive Programming with Swift book is a really good start
- SwiftUI: Combine: Asynchronous Programming with Swift book should help you to take advantage of it
At the end my recommendation is to read both 
in order of appearance, By exploring how different frameworks apply their own solution to the same topic will expand your skills and you’ll be able to see the big picture of it
Curiosity is your best friend
Hope it helps
Good Luck! :]