Benjamin wasn't exactly reading -- but he was being creative and clever. Toddlers as young as 18 months might start to page through a book and babble, but by age 2, they do some sophisticated fakery. They can recite specific parts of a book from memory, summarize the plot, or make up their own stories based on the pictures. By 3, some kids are able to memorize entire books word for word.
There's no research that proves that children who do this learn to read more quickly than those who don't, but it does indicate a strong interest in books. Plus, when a child "plays" with words this way, it's a reflection of how much Mom and Dad have been reading to her -- which also nurtures a love of the written word. So the next time you catch your toddler leafing through The Very Hungry Caterpillar and narrating the action on the pages, encourage her: "Wow, you know exactly how that story goes. I'm so proud of you. Can I hear more?" Chances are, down the road, you will.