It all depends on how much experience you have already, and which books you have read already.
How much Java8+ do you know?:
The one book I would recommend for everybody is Effective Java by Joshua Bloch. The most recent edition was in 2017.
I just did my OCP and now I am reading Modern Java In Action, which is fun to read. There is some overlap with the OCP material but that doesn't bother me at all. Or the Java Module System could also be an option maybe?
It mainly depends on you and what you want to learn next. There are also plenty of nice books on Design Patterns, Java EE, Spring, etc...
Oracle Certified Professional Java SE 8
Power corrupts. Absolute power xxxxxxxxxxxxxxxx is kinda neat.
Building a Better World in your Backyard by Paul Wheaton and Shawn Klassen-Koop