“The "I" who speaks in this book is by no means the author. Rather, the author wishes that the reader may come to see himself in this "I": that the reader may not simply relate to what is said here as he would to history, but rather that while reading he will actually converse with himself, deliberate back and forth, deduce conclusions, make decisions like his representative in the book, and through his own work and reflection, purely out of his own resources, develop and build within himself the philosophical disposition that is presented to him in this book merely as a picture.”

On War (1832), Book 2

Revised edition, 1985. p. 175.
Ceremonial Chemistry (1974)

Source: Journey Within (1947), Ch. 2 : The Three Revelations
Context: No one ever reads a book. He reads himself through books, either to discover or to control himself. And the most objective books are the most deceptive. The greatest book is not the one whose message engraves itself on the brain, as a telegraphic message engraves itself on the ticker-tape, but the one whose vital impact opens up other viewpoints, and from writer to reader spreads the fire that is fed by the various essences, until it becomes a vast conflagration leaping from forest to forest.

Source: Speech at banquet given by the city of Glasgow to Disraeli on his inauguration as Lord Rector of Glasgow University (19 November 1870), cited in Wit and Wisdom of Benjamin Disraeli, Collected from his Writings and Speeches (1881), p. 16.

Tout livre a pour collaborateur son lecteur<br><br>Source: Biographical notice http://www.evene.fr/celebre/biographie/maurice-barres-499.php on Evene

Book V, Introduction
Variant translation: It may well wait a century for a reader, as God has waited six thousand years for an observer.
As quoted in The Martyrs of Science; or, the Lives of Galileo, Tycho Brahe, and Kepler (1841) by David Brewster, p. 197. This has sometimes been misquoted as "It may be well to wait a century for a reader, as God has waited six thousand years for an observer."
Variant translation: I feel carried away and possessed by an unutterable rapture over the divine spectacle of heavenly harmony... I write a book for the present time, or for posterity. It is all the same to me. It may wait a hundred years for its readers, as God has also waited six thousand years for an onlooker.
As quoted in Calculus. Multivariable (2006) by Steven G. Krantz and Brian E. Blank. p. 126
Variant translation: I am stealing the golden vessels of the Egyptians to build a tabernacle to my God from them, far far away from the boundaries of Egypt. If you forgive me, I shall rejoice.; if you are enraged with me, I shall bear it. See, I cast the die, and I write the book. Whether it is to be read by the people of the present or of the future makes no difference: let it await its reader for a hundred years, if God himself has stood ready for six thousand years for one to study him.
Unsourced translation
Harmonices Mundi (1618)
Context: Now because 18 months ago the first dawn, 3 months ago broad daylight but a very few days ago the full sun of the most highly remarkable spectacle has risen — nothing holds me back. I can give myself up to the sacred frenzy, I can have the insolence to make a full confession to mortal men that I have stolen the golden vessel of the Egyptians to make from them a tabernacle for my God far from the confines of the land of Egypt. If you forgive me I shall rejoice; if you are angry, I shall bear it; I am indeed casting the die and writing the book, either for my contemporaries or for posterity to read, it matters not which: let the book await its reader for a hundred years; God himself has waited six thousand years for his work to be seen.

New Epilogue, p. 1214 (See also: Karl Marx - History - Statistics...)
Main Currents Of Marxism (1978)

p, 125
Other writings, The Paradoxes of Legal Science (1928)

Metaphors of Reading, p. 168.
A History of Reading (1996)