Short answer: replace generic adjectives ("passionate," "expert") with verifiable facts: years of experience with the topic, relevant background, previous publications, or any credential a reader (or an algorithm) can cross-check.
Experience, Expertise, Authoritativeness, Trustworthiness — the framework Google uses (documented in its quality rater guidelines) to judge whether content comes from a trustworthy source on the topic.
The author page's bio, Amazon's "about the author" section, and the Goodreads author profile should consistently repeat the same verifiable facts — coherent repetition across platforms strengthens the signal.