Well yes… learning C++ or any other similar language is surely going to help since blueprints is still programming.
I already knew some unrealscript and some C++ before I got into UE4 and learning blueprints was really easy to understand.
But practice is the way to go though, don’t just read but write code… it might be just me but books didn’t got me very far… it was when I started to actively writing my own code every day little by little and modify existing code that I actually started learning.
A generic C++ book however might have some useless information that you might not need to ever know to be able to program in UE4.
If you want to learn C++ just so that you can understand blueprints better, then I think that would be a waste of time… it should be better to simply focus on blueprints or learn a more simple language like Java or C#.
If you want to seriously get into programming in UE4 then definitely get into C++ since sooner or later will find a lot of limitations in blueprints (plus you will be able to make your own blueprint nodes if you need to).