Similar story here, I played with C++ back in 1998 and then again in 2007.

After reading these two books it definitely changed the way I see and work with C++, I fell in love with it.

So reading old code-bases is very common, you still need to understand the old C++ anyway:

Professional C++, Wrox, Jan 2005

Then to get yourself up to speed with C++11 and C++14:

Professional C++ 3rd Edition - Wrox, Sept 2014