If you've just started, well, yes you'll probably need some books/lessons to tell you how to find your way around the guitar, what some chords are etc. and you'll have to work hard at it to get your technique up to a reasonabe standard. However, from that point, a good way of widening the range of what you can play, and also improving your technique without you really noticing it, is to work out how to play songs you like on the guitar. This will also work wonders for your general musicality and stuff. This is what I do, I've never had lessons, and every time I hear a nice bit of guitar playing I make a mental note of it, then when I get home I work out how to play it, just by listening to it over and over on my computer. It's really good for improving your guitar playing, and of course it means you'll know how to play all your favourite songs!
