I'm not sure how C++ for DL is different from regular C++ so take my advice with a grain of salt.

I took a class under Bjarne Stroustrup and he highly recommended Tour of C++ [0] as the best way to learn modern C++ for someone who already has some programming experience. That and of course, Effective C++[1] by Scott Meyers.

[0] - https://www.amazon.com/Tour-C-Depth/dp/0321958314

[1] - https://www.amazon.com/Effective-Specific-Improve-Programs-D...

Get this - https://www.amazon.com/Tour-C-Depth/dp/0321958314. If you are stuck at any point ask on /r/cpp, people there are very friendly and knowledgeable.