The book title is a bit misleading. It should be "Functional programming in kotlin" as the book follows structure and content of "Functional programming in Java" and "Functional programming in scala" from the same publisher.
I might be biased, but out of those 3 (fp in scala, java, kotlin), I've enjoyed scala version the best. Perhaps because scala is truly function programming language, while kotlin is more"pragmatic java" kind of a deal, which coincidentally makes it more functional.
You should expect basics of functional programming from this book: pure functions, persistent data structures, lazy evaluations, folds, recursion and corecursion, etc.
The books tries to be very gentle and slow with introduction of new concepts (and doesn't use category theory language), but requires you to do a lot (and i mean "A LOT") of exercises. If you're not familiar with functional programming I highly recommend doing it.
On the other hand, if you did your homework with SICP, i don't think this book will be enlightening in any way (while "functional programming in scala" by Rúnar Bjarnason might still be lots of fun and discoveries)
As with all books in this series, you might end up being lost at the end. "I got it how to make my code more functional, but how is this applicable to my day job?"
For those folks a i would recommend "Domain Modeling Made Functional: Tackle Software Complexity with Domain-Driven Design and F#" by Scott Wlaschin and "Functional and Reactive Domain Modeling" by Debasish Ghosh.
Between 3 and 4. It's not a bad book.