http://www.gutenberg.org/etext/32769
This looks nice too, but I don't know this author at all.
The last generation by James Elroy Flecker [Short story]
This looks perfect for the Short Story collection (or the Sci-Fi one, actually) ... it's split into sections, but overall it's under 7K words, so would come in at about 40-50mins.
There's honestly no such thing as a stupid question -- but I'm afraid I can't rule out giving a stupid answer : : To Posterity and Beyond!