According to this review of The Affirmation of Life: Nietzsche on Overcoming Nihilism Benjamin Moritz says that Bernard Reginster has a persuasive argument about the significance of the will to power. Reginister, Moritz, says:

places the concept’s development within the context of Schopenhauer’s thought and carefully traces Nietzsche’s subtle alterations of various constituent parts. In particular he notes that Schopenhauer believed that human willing was doomed to failure because of the unsatisfactory nature of the relationship between desires and objects. Specifically, Schopenhauer bemoans the fleeting nature of desire satisfaction and the looming problem of boredom. Reginster argues that Nietzsche’s concept of the will to power is a direct response to and critique of Schopenhauer’s views. Whereas Schopenhauer concentrated almost exclusively on first-order desires, Nietzsche establishes and defends second-order desires: the will to power.

Moritz, says:

Reginster finds a place for the will to power within Nietzsche’s philosophical system, without focusing on it as an end in itself. Its place is to serve as justification for life’s suffering. By establishing a second-order desire—the will to power—as the highest value, the paradoxical nature of a desirable life that simultaneously includes suffering is remedied. Through desiring the process of overcoming (a simplified but largely accurate reduction of Reginster’s conception of the will to power) one can desire suffering without falling into the asceticism that Nietzsche loathes. Subsequently, the acceptance of this newly revaluated state of affairs lies at the core of the eternal recurrence.