For me, the hardest part about OTP is not the syntax (how to use it), but understanding why and more importantly when to use it.
When you feel ready to really go down the rabbit hole, Designing for Scalability with Erlang/OTP thoroughly explains the how and why of OTP behaviours, how Erlang messaging / distribution works, and plenty of other things that are useful when building “distributed, fault-tolerant, scalable, soft real-time, and highly available” systems.
It’s an awesome book, but does require that you learn to read some Erlang if you want to follow along with the examples.
