I think this is a just sign of being really excited to read a lot of books. Presently, the world constantly throws headlines and short articles at you, and in turn, you read them and move on to the next one, forgetting most of what you read about yesterday or last week. Longform writing and books that demand my attention are some of the most rewarding experiences I have ever had. There is nothing quite like finishing up a great novel. I used to get the feeling you describe a lot and I occasionally get it now. This feeling usually creeps-in after I browse through my stacks of books or visit the bookstore/library then return to my current book.

What has helped me is to realize that I probably felt the same way about the book I'm currently reading while I was reading the previous book. It's a feeling of unsatisfactoriness that rears it's head quite often. To get rid of this feeling, I tell myself that the other books don't matter and go ALL in on the character and situation happening in my current book. I read the next few pages carefully with all my presence and usually this is enough to get me back in the zone and the pages fly by. I refocus whenever I feel I'm trying to finish a book to move on to the next.