Large-Scale Scrum: More with LeSS  

Amazon

I've worked with Scrum teams for quite a while now, and whilst its a great process for delivering software, when you keep on expanding to more and more teams working within the same product then things can start to get messy.

LeSS is a great framework for just taking your existing scrum processes and scaling them, no HUGE changes or loads of training courses needed (looking at you SAFe).

This book was a very interesting read and definitly helped me to evolve Scrum practices that I use. I'd highly recommend it.