some info
Here's a few tidbits to chew on.
I have a college degree in voice...I say that not to be a jerk off or because I think I'm cool, but just so you know there is at least some credibility in what I'm saying.
If you seem to be getting tired quickly when you sing, that's annoying, but ok. The voice is a very small muscle in your throat, and just like any other muscle in your body it gets tired and needs rest. It also gets stronger the more it gets used and fatigued, again like any other muscle. So the best thing you can do, is keep singing. Work the muscle so it stretches and gets stronger. It may take some time, but you'll find your strength, range and stamina will improve with time.
NOW... that being said. If you're experiencing pain, that's a whole other story. Your voice should never hurt. I mean...it will (that's inevitable sometimes) but if you want to sustain a long career as a vocalist, pain is not good.
Of course (here's another caviot) if you're going for a real raw or screaming, or death metal sound, you're probably not too worried about the quality of your sound as much as the emotional product you push through the microphone. If that's the case, go for it. Do whatever you want.
But because you posted, I'm assuming that's not you.
The reason I say pain is bad is because if you're having pain, it's likely your voice is not functioning like it should. There's probably swelling or even worse going on in there. You should stop singing, and if possible, talking as much as you can.
The consequences: over time if you continue to experince pain when you sing, you could deveop callouses on your vocal chords. This is bad. It can make your singing and speaking voice raspy and parts of your range disappear altogether. AND it's VERY difficult to fix. You basically have to fully rest your voice for weeks and hope it works.
And it gets worse...if it gets too bad, there is a real possibility that you can blister your vocal chords. If this happens, the blister will heal into scar tissue and you're permanently jacked up. You can have surgery to rapair it, but even the surgery leaves some scar tissue and you'll never be the same.
So, in short: if your tired: fine - you're getting a good workout. If it hurts: stop now, or you could be in trouble.
As far as books or stuff to help you with technique, I'm really not familiar with any. That's not to say they don't exist, I just don't know about them.
The best advice I have is keep working, try to relax when you sing and if possible, get a vocal coach. A good one. One that won't cram opera or classical voice down your throat, but that cares about the biology of your voice.
That's my dissertation. I hope something helped.
chris
