Why can't I read book when I'm inside a house?

This may sound weird but I find it difficult to read books when I'm inside a house; it's like I can't focus and the book doesn't grab my attention. On the other hand, when I'm outside, in the park, sitting on a bench, or at school, in the library, or anywhere else in the world, I can devour a whole book in a few hours. What's up with that?