Learning c++ syntax is only the beginning. Now you know the words, but you need to learn to put them together to form sentences, paragraphs, etc. C++ knowlege is not something you acquire through "volumes." It is your ability to solve problems that will make you a far better programmer. I can tell you from experience that I've had many times where I was stuck at a particular problem, not because of my knowlege of c++, but because I didn't really understand the given problem. And learning how to solve simple things such as: figure out how inheritance works for a animal, dog, german sheppard scenerio does not count. Sadly, this ability is something you gain from experience, and that is what you need to keep after. Find interesting problems in math, chemistry, physics, engineering and try to implement solutions for them as c++ programs. This will force not only to program, but also to problem solve.

For a second book, I will recommed that you buy one that covers data structures in c++ and make sure you understand the concepts. You might want to pick up a book about the STL library in c++. Here are some suggestions:

Data Structures and Algorithms in C++, Second Edition
ISBN: 0534375979

The C++ Standard Library: A Tutorial and Reference
ISBN: 0201379260

Good luck

C++ for Game Programmers by Noel Llopis is a good second book for someone learning to program games. It assumes you know the basics of C or C++ already and teaches you thinks like efficiency and design patterns. It's not really about how to make a game, it's about how to make the code for your game better. I have to say that this book helped me so much more than any "introductory" book on OpenGL or DirectX. In fact, those beginning opengl and dirctx game programming books seem much simpler after reading it.

Game Coding Complete 2nd Edition by Mike McShaffery is a great book to follow up C++ for Game Programmers. It covers the bigger picture of programming a game besides just the graphics and each chapter covers a different subsystem in detail. I'm still reading this one, it's densely packed with code examples, advice, potential snags, and anecdotes from a veteran game programmer who's seen it all. Easily the best game programming book on my shelf, and I have quite a few.

You should also pick up Data Structures for Game Programmers by Ron Penton. Data Structures really arn't the most exciting thing to study but understanding them is an important fundamental step toward being a game programmer. The author does a good job of keeping this thick and heavy book readable and keeping it directed toward games.I think every programmer should read Code Complete 2nd Edition by Steve McConnelll. It's not about a single language, it's about the proper practices to programming in any language. Maybe not a great second or third book but a very valuable read.

As for a definitive answer on whether DirectX or OpenGL is better, there just isn't one. It really depends on what game you are making and what platform you are making it for. You'll learn how to keep the game logic seperate from the rendering so that a renderer could be swapped out when needed. If you've never made a game before it might be a good idea to start with something simpler for the graphics like SDL or an existing game engine. You should choose your renderer because of the features if offers that suit your needs best not because someone else told you it was the one to go with.

I think you're better off learning about all of the components of a game and strengthening your overall programming skill before you get into the specifics of drawing those images on the screen.