Book Recommendations
I like books as the longer format allows for more complex topics to be covered in a structured way. Digital books are a huge help as searching text is so much easier that remembeing where that thing was discussed in a paper book. All of the books listed below have a digital version or are exclusively digital.
Buy what you need when you need it, unless there is a sale! If you have just finished 100 Days of SwiftUI, then the Big Nerd Ranch book is a great way to learn about UIKit. Then grab the free version of Big Mountain Studio's SwiftUI Views Quick start and go from there.
Big Nerd Ranch
iOS Programming: The Big Nerd Ranch Guide
Grab a mac, fire up Xcode and crack open this book to learn swift and iOS programming with UIKit. The 7th edition is a little dated, but it is a great introduction to UIKit. I got the Kindle version and it was under $25 and is formatted fine with the macOS Kindle app.
Mark Moeykens' books are written like a well annotated Keynote presentation. They are very visual and go into detail with many many code examples. Check out his free SwiftUI Views Quick Start for an idea. I recommend all of his books.
Combine Mastery in Swift
Combine Quick Start in SwiftUI
Concurrency Concepts
SwiftUI Animations Mastery
SwiftUI Views Mastery
Working with Data in SwiftUI
Donny Wals published two books. I've only read one, which was Practical Core Data. It was very helpful and solidified Core Data concepts for me which allowed me to use them in an app.
Editor's Cut - Daniel H Steinberg
If you have seen one of Daniel's talks then yoou have a good idea of what his books are like. Each section walks the reader through the motivation for the concepts being taught. He even has a book on baking bread. I recommend all of his books.
A Combine Kickstart
A Functional Programming Kickstart
A Swift Kickstart
A SwiftUI Kickstart
Async Cafe (currently in beta)
Bread Baking Kickstart
Natalia Panferova
Integrating SwiftUI into UIKit Apps is about integrating SwiftUI into a UIKit application. This is something that will continue to be needed for quite a while and found this book practically minded and helpful.
Hacking with Swift - Paul Hudson
Paul is a prolific creator of content. In addition the the hundred of articles and videos on his site, he also has 21 books on sale. While I have them all (those bundles are hard to resist when you hit a sale), I've not read them all. The one's I have read are helpful and are not just about getting a formulaic answer. Some of his books I found helpful are:
Understanding Swift
Pro Swift
Objective-C for Swift Developers
Beyond Code
Pro SwiftUI
Testing Swift
Swift Design Patterns
Swift Concurrency by Example
Dive into Spritekit