I used to be in a hard rock band, with another guitarist. I was self taught, and he took lessons. He had been playing half as long as me, and yet he could leave me in the dust when it came to guitar solos. He was quick, precise, and could practically play a song as he was reading the tab for it. However, I had a wider knowledge of music and how to apply it to songs, since I had to figure out everything on my own. I could easily piece a song together by ear, or come up with an accompanying riff off the top of my head. These qualities made him a great lead player, and me a great rythm player. Neither technique is "better", they just lend themselves to different mindsets.
I have the "rock guitar for dummies" book and its actually a great read for players of all skill levels. Not only that, but the dude covers just about ANYTHING you could possibly ask. I would get it or any of the other "for dummies" books for sure.
I learned mostly on my own after a few initial lessons, and I got along fine. 4 years later, all of my friends complimented me on my different approach to playing. It got me a great position as a rythm guitarist in a band, because I had a hard hitting sound that let the lead player do whatever he wanted and not have to worry about me (I was the "Malcom" and he was the "Angus"). Learning on your own tends to let you develope a unique style of playing, and helps keep you from playing just like every other guitarist out there.
However, I did pick up some bad habits that I didnt realize I had until I started teaching other people how to play. For the love of god, make sure you learn alternate picking, and how to do it right. I was too lazy to learn it on my own and I'm sure as hell paying for that now. You also will find it takes much longer to learn this way, as you have to figure out almost everything on your own. Use youtube, or other video sites as much as possible. This way you can hear if a song or technique is wrong when a guy is describing it. Relying on tab when you're just starting out is a horrible idea, because 9 times out of 10, that tab you are playing will be wrong.
Its really up to you though, if you've got the discipline and patience, teach yourself. But if you're having trouble, or get frustrated easily, lessons will deffinitely be a good investment.