A Gambler's Caveat and Gratitude

Here are a couple of unusual reader inscriptions found within a few pages of each other. 

In a copy of The Greatest Gamblers: An Epic of American Oil Exploration, by Ruth Sheldon Knowles (McGraw-Hill, 1959), the book's owner first felt it necessary write a brief inscription to the borrower, reminding him that the book was expected back.

To: Dr. Hood (but not for keeps), Jim

I've never seen a book with a "loan note" in it like this. Was there something implicit in the book's title that rendered the loan a gamble? Was there a precedent for this with Dr. Hood? Or was Jim merely eliminating any ambiguity associated with presenting his book to Dr. Hood?

Regardless, this reader inscription  tells us that Jim valued this book and wanted it to stay in his collection.

The owner of the book, Jim, soon reveals that he is one of the gamblers in the title and contents of the book. About three pages later, the author's dedication reads as follows:

To all the unsuccessful explorers who

have drilled America's 300,000 dry holes

and whose failures have guided others 

to the discovery of an abundance of oil, 

I dedicate this book with gratitude 

and admiration for their courage, venture-

someness, faith, persistence, and optimism.

Underneath the dedication, it appears that Jim has written his own expression of gratitude for the author's recognition. His reply reads simply, Thank you, JGS.

I've never seen this before, either--a reader's written response to a book's dedication. One could (and probably should) assume that a sarcastic thanks is inferred, given the context of the dedication and further assumption that Jim was one of the wildcatters who drilled a dry hole or two.

Perhaps this gambler was just hedging his bet when he loaned this book to his friend or colleague, Dr. Hood, with the caveat "not for keeps" to ensure it was returned.