Such a coincidence that you wrote about this today! I just wrote a post on my blog about this with son.

He actually read his first book independently just a few days ago (at three and a half) but even though that�s early, he�s been perfectly capable of doing it for months, and just never wanted to on his own. He�d read full sentences with no problem at the pocket chart I bought for him, and he was also writing short words already. but whenever I�d ask him to take a shot at reading (things I knew he could) off of the page of a book, he�d always just want me to do it. It was just so odd to me because he is SO into his books (he�ll make me read like ten of them in one sitting, or a whole chapter of Harry Potter); you�d think finding out he was capable of reading from a book on his own would super-excite him, but it really didn�t.

You know what did the trick? His six year old friend coming over to play and reading an easy-reader to him� Every few pages, she�d get stuck on a word and he�d tell her what it is. That night, he read the whole thing with me, word for word� and the day after that, he read it on his own, and started reading a couple of others on his own, too! (I always tried the pausing trick, too, and pretending I needed help figuring out a word. Sometimes it worked, but never like it did when his first grade friend really actually did need help.)
(If you�re interested, my blogpost about it is on aliciastucky.blogspot.com)

I agree with SiaSL. Even after he learned that he could read books on his own, he was adamant about making sure I would still read to him a lot, too. I wonder now if that fear was holding him back, or something. I make sure now to set aside different times for both activities: reading to him, and then reading together.