Jenseits von Gut und Böse: Vorspiel einer Philosophie der Zukunft, 1886. Recommended translation: Beyond Good and Evil: Prelude to a Philosophy of the Future, trans. Walter Kaufmann, Random House, 1966.  

Excerpt:

The will to truth which will still tempt us to many a venture, that famous truthfulness of which all philosophers so far have spoken with respect—what questions has this will to truth not laid before us! What strange, wicked, questionable questions! That is a long story even now—and yet it seems as if it had scarcely begun. Is it any wonder that we should finally become suspicious, lose patience, and turn away impatiently? That we should finally learn from this Sphinx to ask questions, too? Who is it really that puts questions to us here? What in us really wants “truth”?

Indeed we came to a long halt at the question about the cause of this will—until we finally came to a complete stop before a still more basic question. We asked about the value of this will. Suppose we want truth: why not rather untruth? and uncertainty? even ignorance?

The problem of the value of truth came before us—or was it we who came before the problem? Who of us is Oedipus here? Who the Sphinx? It is a rendezvous, it seems, of questions and question marks.

Online:
Amazon (Recommended Translation)
Nietzsche Source (German, Free Access)