It's also possible that HIS reading is too slow for him. It might frustrate him because it takes too long & he misses the meaning while struggling with decoding. This is why I advocate that even with the most advanced reader, you don't stop reading TO your child.
Well this quote from bluemagic is my best guess about what was going on with my DS8 who sounds very similar to your son. He has always enjoyed being read to, and we still read to him on a daily basis. He was basically not reading on his own at all at the beginning of first grade. We were working with a stealth dyslexia assessment although I , like you, felt there were a number of things that seemed to make it a bad fit for DS.
Then, over a period of a few weeks he went from not reading on his own at all to reading on his own voraciously. And with seemingly no upper bound on level of material. (He does still mispronounce all sorts of vocab - but his mispronunciations are usually phonetically correct.)
Now he is one of those kids who loves reading to himself. He always carries a book along, and will stay up as late as we'll let him to do it. We do still read to him, and he loves that, too. But he'll often pick up where we stop and, for example, finish a book with a flashlight under the covers.
I really think it was a matter of some things clicking into place. Once all the (asynchronously developed) bits were in place he just "knew" how to read. So long as our reading to him was faster than his own reading though, he preferred that. As bluemagic put it, until that point, his own reading was too annoyingly slow and it was just inefficient.
Of course you should check out the vision and other issues folks on this board have pointed out. But if none of them bear fruit, you might want to consider just giving him a little more time, while enjoying being able to read to him a bit longer.
Sue
P.S. DS would NEVER have been willing to read museum labels and such. He still wouldn't even though he has no problem with it. Too close to a dog and pony show activity for him and he relentlessly avoids that. Even if it's just his dad and me there. I wouldn't push that if your DS is at all like that. You could, though, try to get him to read to you when it's more of a "necessary" thing. DS will sometimes read to me when I'm cooking or folding laundry or driving - e.g., when it's not possible for me to read the material myself.