For kotlin, no book needed.
Go to the language website, read the introduction, maybe a couple of pages on the language features and then complete the kotlin koans. It will give you an overview of most of the language features.
After that, find an android project written in kotlin.
Here is one : https://github.com/LostInContext/LostContext-App (there are many others) .
Configuring an android project in kotlin the first time can be painful, especially if you have some code generation (dagger, databinding, ...) , so it is way easier to have a working sample to work with.
For kotlin, no book needed. Go to the language website, read the introduction, maybe a couple of pages on the language features and then complete the kotlin koans. It will give you an overview of most of the language features.
After that, find an android project written in kotlin. Here is one : https://github.com/LostInContext/LostContext-App (there are many others) . Configuring an android project in kotlin the first time can be painful, especially if you have some code generation (dagger, databinding, ...) , so it is way easier to have a working sample to work with.