Welcome to the obsession, Miguel ;). I started writing online on a similar community-based writing site, and it ended up being one of the best things for my writing career. It doesn't directly help you write a book or get it published, but it is full of people who can help offer tips on how you can polish your writing. If you let your readers know in your hubs that your intention is to eventually publish books, they are more likely to leave constructive comments toward that end.
This site can also help you get an audience. Once you have a base of people who like your writing, it gets a lot easier to get the kind of feedback and support it takes to write a book.
So yes -- Hubpages gives you practice, feedback, an audience, and maybe a little income during the journey. I say "maybe" because I think you have to be 18 to get a payout, but that gives you some time to work on it until then. I started writing online part-time when I was 15 (okay, I might have lied about my age a few times, but shhhhh...never did lie to Hubpages :P ), and went full-time six years later, in 2007. Today, writing feeds my family of five. I've only ghost-written books so far, all client work, open-submission and my own domains rather than actually putting my name on the cover, but it can certainly help if a book of your own is the goal too.