It's subjective to say what the best book podcast is, as it ultimately depends on personal preference and interests. However, some popular book podcasts that are highly recommended by listeners include "The New York Times Book Review Podcast," "What Should I Read Next?," "The Book Review Podcast," "Reading Glasses," and "Literary Friction." These podcasts cover a wide range of genres and topics related to books, and offer insightful discussions, author interviews, book recommendations, and more.