The wall in a book

One thing that I sometimes have a hard getting over is when you read so far into a book at some point it becomes for whatever reason very hard to read, its a bit like the wall that marathon runners talk about, why this should happen to readers of books or just to me I just don't know, but the fact remains that there are books out there that for one reason or another have this wall, so far very few of the books with this wall have I failed to finish.

That's not to say that there are books that I have failed to complete, there are few and far between, some of the books are by authors that have had big hits.