My dd became a solid reader just around her second birthday, and most of her speech development was aided by reading. Early on I sought out forums like this because it seemed pretty freaky. In her case, she started early and never slowed down. By 4yo, she stopped wanting us grown ups to read to her because she could read faster on her own. We followed her obsessions (dinosaurs, horses, Star Wars, etc.) and found *every* possible book for her to read. The public library has saved us many thousands of dollars as we indulged her obsession with books. She reads way faster than me and I envy her ability to go through a long novel in just a few hours. For several reasons, we never did a whole grade acceleration and do not regret that decision. She is now 15yo and just finished 9th grade (at a high performing public school with many professor's kids), at or near the top of every class she took, with plenty of time for extracurriculars and socializing, right up to finals. She has been subject accelerated in math since 2nd grade, and just finished her first year of calculus.
We did have some concerns about hyperlexia when she was 2yo - i.e., that reading was a savant skill without comprehension. It turned out not to be an issue for us, but it is something to look for in very early readers. Excluding cases of hyperlexia, I think most cases of extreme early reading are like ours, in that it is an early sign of an extremely capable learner.
