I recently found a book on Amazon that I believe is only printed on demand. It's not found in any library, that I know of.
This book is a collection of letters sent to my great-great-grandfather, after the death of his wife. The index contains a list of names of those whose letters are included in the book. So I created a free space page for the book. Since it is not in copyright, I could email a copy of a page to anyone who wants one. I have found a few profiles already here on Wikitree. If you have any ancestors who were missionaries to China, you may want to take a look at the free space page.