Yes, it is possible to read too much. I see it all the time here at the library. A patron will come in and plop a book down on the counter and exclaim, "I read two pages and realized I read it already!"
I always reply, "That's a sure sign that you read too much!"
Some of our readers come prepared, though. You always see them with a stack of books and a little notebook with every title they've ever read written down in it. This way, they'll know if they've read something already.
Of course, you could ask to have your reading history kept in our computer system. But beware, we have to warn you that the government can come in at any time and request to read your history. We always let people know this fact if they choose the reading history option on their library card application. One woman replied, "Oh, I'm sure if the government wants to see what I read they'll find a way to do it anyway!"
Still, with these two options--the journal and the reading history choice-- some people still choose to "wing it" when they come in and run the risk of taking home books they've already read.
Though it happens frequently. I'm still amazed every time I hear someone say that they didn't realize they'd already read a title. I start to wonder how many books a person would have to read to have this happen. Then, one day it happened to me. I was reading "The Twelfth Card" by Jeffery Deaver and, even when I finished it, I couldn't remember if I'd read it before because I couldn't remember the ending. Honestly, I still don't know. (It was a great book, though.)
So, if you find yourself reading a book and thinking, "My, this sounds familiar," maybe you've read it before...and, maybe you read too much. But, hey, I'm a librarian, so I'm always gonna think that reading too much is a good thing!