This was an interesting analysis. I noticed that it says 200 pages for Metamorphosis, my copy (W W Norton) is 126 pages of large print, including a forward and afterword. It's really a short story.
Also, though I suspect it evens out, personally my reading speed varies a lot depending on the author. Orwell, or ironically Kafka reads pretty fast. Something like the Brother's Karamazof (which I've started twice and failed to get anywhere with) I have to read way more slowly.