I'm curious how up to date those books are with the latest version of Play/Slick, given how fast conventions move in those projects. The Play book seems to be from 2015, that sounds quite outdated.
There are only two significant things that are out of date. A minor tweak in the JSON library and the new DI system. The former is an easy fix. The latter will require a new chapter. I'm happy to chat to anyone who is interested in collaborating on these parts.