Elders Secret Book
The Watchtower Bible and Tract Society of Pennsylvania publishes a book called;
Pay Attention to Yourselves and to All the Flock © 1991.
Only active elders may possess a copy of this book, and they are instructed not to lend it to anyone who is not an elder. Although the existence of this book is arguably obscure among non-elder publishers, pioneers, and newly interested ones, the fact that this book exists is not a secret. Just ask any elder, and more than likely they will happily confirm the existence of this book and verify that they have a copy in their possession.
However, since only elders may read the book, the contents of the book are, by definition, secret.
The Watchtower Bible and Tract Society of Pennsylvania strictly controls this book, and have been know to use the full extent of copyright law, or at least, the threat of litigation, to prevent any authorized use, study, or viewing of its secret contents. Attempts by some to publish this book on the World Wide Web have resulted in litigation from the Society's legal department. Clearly, this book is unique among the extensive library of Watchtower Society books, as it is not handed out on street corners and not delivered door-to-door.
However if you would like to see the content of the book a search on Google with Pay Attention to Yourselves and to All the Flock should quickly bring it up.