Effective Modern C++ by Scott Meyers is a good book that I've been supplementing with google searches. It goes over the main new features in '11 and '14 you would want to know.
+1 for this book. Also, if your company can afford it, having Meyers or Sutter coming on site to give a day or two lecture to a group about Modern C++ is worth it. They both have great handout material, give great lectures/presentations and are very approachable with (even idiotic) questions.
(disclaimer: I am an unattributed - due to company policy - interviewee for Meyers Effective Modern C++)
Aw, damn. It's been before 2014 I last saw him in person, so I have no idea. It's a shame, because he is a great presenter with an infectious energy about him that I found really engaging.
I can confirm that this book is a great starting point, having undertaken a similar project last year. Off the top of my head, the biggest change is move semantics, along with smart pointers. Once you have those concepts down the other pieces are comparatively quick to pick up.
I've always liked C++, but I think it's become a much more enjoyable language to use in the last decade.
Oh, while you're at it, check out the Passkey pattern[0], which is a nice way to avoid overuse of friend classes.