I actually felt something like this today! I recently bought two of my childhood favorites at a second hand bookstore. Last month I reread the first and I was a bit disappointed. It just wasn't the same magical adventure anymore, even though most of my other favorite books from that time still hold up. Today I started rereading the second one and so far, it's been great, to my immense relief. But it also made me a bit melancholy, because I miss the way reading felt when I was a child. I've never stopped reading, I've discovered some absolutely amazing books in the past few years and continue to do so, but it's different. I don't even mean it's worse, I still enjoy reading as much as I did back then, but there's just something magical about reading when you're a child and that magic is definitely gone now.