Size matters

So, I was walking through my bedroom slash office getting something, and my eye happened upon some books, and I saw what I thought was an interesting juxtaposition. As usual, I over-thought it, and gathered more samples, and anyway, herewith are the results:

The two tallest books in my bookcases:

The two thickest books in my bookcases:

The two smallest books (by surface area of cover) in my bookcases:

I'm not sure what meaning I can glean, but there it is.