Atomic Kotlin is the book and associated learning resources by Bruce Eckel and Svetlana Isakova.
Version 1.1 (November 2021) includes updates for Kotlin 1.5 (works with 1.6) and all corrections/clarifications since the original release.
Announcement during the October 2018 KotlinConf opening keynote:
Post from LinkedIn
The cover of the print book: