DnD is seriously a great game! I was in your shoes about 6 months ago, I was poking about at a car boot sale, and some guy was selling 1st edition DnD books for a £1 each! Bonus, I thought. Took them home and sat down to read them, pages of charts and gobbledygook! So I looked into a bit further, and discovered that the 4th edition had just been released, then came the big challenge, getting people to play. Being a devious git, I waited until my group of friends all arranged a big night out, we got s**tfaced, and I went round the group one by one, asking them if they would like to play, and got an overall positive response, now 6 months later we rotate our Dungeon Masters and write all our own quests!
It can be expensive to start from scratch, you'll need a Player's Handbook, a Dungeon Master's Guide, and the Monster Manual, which are called the 'core books', because they're what you need to play the game.
Character creation can be a ball ache, but the Wizards of the Coast website has a useful program for making characters which is regularly updated to include all the new material they keep releasing (Monk ftw!), and makes things a lot easier for beginning players.
Then there are tonnes of supplements and add-ons for you to use, such as fully prepared quests (which are fun, but try writing your own, it feels more personal and you can really tailor it to your gaming group), dungeon tiles (which let your create your own custom dungeons), and full blown expansion packs like Eberron, Forgotten Realms and the newly released Dark Sun (which sounds awesome!)
Like I say though, all this is expensive, but it's worth it when your group all comes together and you end up rolling about laughing at the camaraderie.
That's about the tip of the iceberg though, but I heartily recommend it!