Arrow comprises different libraries, each improving or extending one commonly-used library in the Kotlin ecosystem or a particular Kotlin language feature.
I've been playing around with Arrow V2 for a while and it's really nice. I like the simplifications they've done which feel like they remove a lot of bloat without sacrificing the functionality.
I made a sample project with Arrow and http4k. They both work very nicely together. Link here if you'd like to take a look.