What do you want to do?
Learning a language takes a few hours. There's not that many concepts in any of them. They're all share a lot of concepts with each other.
...
Learning new languages isn't remotely hard. Come up with an actual thing you want to make, and make it in whatever language seems appropriate.
Yes and no. There is a large group of languages that are similar as they are imperative with variables and procedures. There are a lot of quite different types of languages. Here are some challenges for you to learn in a few hours:
very not c-type procedural
Haskell (will take more than a few hours to get your head around this) --
https://www.haskell.org
similar, but different: ocaml --
https://ocaml.org
sml --
http://www.smlnj.org
This is partly old history but extremely important still, not learned in a few hours
lisp --
https://en.wikipedia.org/wiki/Lisp_(programming_language)
ooh, this one i love, especially the create ... does words: forth --
http://www.forth.org
or why not good old sql --
http://www.w3schools.com/sql/
check this one:
http://listverse.com/2011/02/17/top-10-truly-bizarre-programming-languages/
/Gunnar
[doublepost=1452079752][/doublepost]Sorry about the digression in my previous post, not really helping the OP.
Personally I would suggest staying away from c++. Really learning that is going to be a quite long and tedious adventure, more on the time scale of several years. In my mind c++ simply is too complicated to really learn unless you aim at getting employment at a fully c++ shop (not too many of those around). It also seems like it is sort off the main line as it is not used much in web development.
If you want to learn low-level basic C, which is good for some things, say embedded computers, the K&R book is the one to go for.
But today, the computer language used really is the small part. The environment with library functions is really the large part. It is different writing for windows, os x, iOS, web browser, web back-end -- all of these rely heavily on calling library functions.
My suggestion then is to select one environment, and learn the details of that one. Select a language much used there and learn the environment together with the environment. Most of us (it seems to me) have stopped buying books as almost everything can be had from the net.
/Gunnar