Volume 3 of Heidegger's gigantic Nietzsche book is concerned with will to power. It interprets Nietzsche as the thinker of the consumation of metaphysics. Heidegger says:
"In the thought of will to power Nietzsche anticipates the metaphysical ground of the consummation of the modern age. In the thought of will to power, metaphysical thinking itself completes itself in advance. Nietzsche, the thinker of the thought of will to power, is the last metaphysican of the West. The age whose consummation unfolds in his thought, the modern age, is a final age. This means an age in which at some point and in some way the historical decision arises as to whether this final age is the conclusion of Western history, or the counterpart to another beginning. To go to the length of Nietzsche's pathway of thought to the will to power means to catch sight of this historical decision."
In Chapter 3 Heidegger quickly cuts to the core of book 3 of Will to Power, entitled 'Principles of a New Valuation':
"Will to power is the 'principle of a new valuation", and vica versa: the principle of the new valuation to be gounded is will to power. What does "valuation" mean? What does the word value mean?....The word "value" is esentialfor Nietzsche....Value for Nietzsche means a condition of life, a condition of life's being "alive". In Nietzsche's thinking life is usually the term for what is and for beings as whole insorar as they are...As a condition of life, value must therefore be thought as that which supports, furthers and awakens the enhancement of life."