A surprise Rube Goldberg piece of cartoonphilately

Does this book, A Night Out by Edward Peple (NY: Moffat, Yard and Company, 1911 5th printing) look like a piece of philately to you? 

I picked it up recently just for the Rube Goldberg drawing of a cat for the cover and frontispiece, which is the only cartooning in it.

 

But when I went to scan it today, I noticed the back cover for the first time.

As you can see, this small book, roughly 4.5" x 7" was meant to be mailed.

And this copy was in fact mailed, or somehow delivered to Mr. C.A. Schwab, Deacons Hospital, Longwood, Mass. Probably hand-delivered since the "Place a Five Cent Stamp Here" block was not used. That postage rate looks good - according to an online calculator, that 5 cent stamp would only cost $1.65 today.

I had originally planned on just scanning the cat and giving the book away, but now I'm adding it to my cartoonphilately collection.

Here's the cat by himself for downloads.