Mostly just reference stuff, didn't bother with all the 'become a master C programmer in 5 easy steps' tutorial type books, as tutorials are plentyful on the 'net. Just reference material for when I see a class or function and don't have a clue what it does, as was the case the first time I ran into an STL vector class and naively thought it had something to do with vectors... which, of course, it doesn't.
First one I got was 'The C++ programming language' by Bjarne Stoustrup, which was frankly a bad choice as it turned out to be a little over my head at the time. It's starting to prove useful now that I better understand what I'm doing though. I also got 'The C++ Standard Library' by Nicolai Josuttis, which I'd say has been rather more useful so far. So if anything, that's the one I'd recommend as while the basic C/C++ syntax isn't all that difficult to grasp, learning all the sometimes obscure built-in functions and classes is a different story.