Our DS went through a very similar stage with reading at about that age, maybe closer to age 5. I remember writing my mother (a former teacher) and saying I was really worried... she said to wait and not to worry. He suddenly started reading a short time later and was through all the appropriate chapter books in our town library (or the ones that interested him, at least) before he was six. There's something different in how he learned to read, although he knew some phonics, he didn't seem to need or respond to practicing that approach. My mom (definitely HG at least, probably PG) said her family said she herself suddenly started reading at about age four or five (after having been read to extensively but not "taught" to read).
