Books that start out by defining their own desired audience/reading conditions

From Clarice Lispector's The Passion According to G. H. – "To Potential Readers: This is a book just like any other book. But I would be happy if it were read only by people whose outlook is fully formed. People who know that an approach – to anything whatsoever – must be carried out gradually and laboriously, that it must traverse even the very opposite of what is being approached. They and they alone will, slowly, come to understand that this book exacts nothing of anyone. Over time, the character G. H. came to give me, for example, a very difficult pleasure; but it is called pleasure."

From the title page to Dash Shaw's Bodyworld – "This book is for "ideal readers" only!!! ...Please read in bed naked."

Descartes to thread

if on a winter's night a traveler, I think ... or maybe he's more just describing the reader getting ready to read

The Brothers Karamazov

Hopscotch

Tristram Shandy does this somewhat, although perhaps not in the initial pages (it would of course be against the character of the book to settle its first matters first).

I read Bodyworld in bed naked! Success!

Me too! I am glad you read it, Mordy. What were your thoughts?