And you put the finger on something right here. As you describe, I didn't see it as: "If I'm sad, I want to listen to sad music".
When I built the app, I was really into that mindset of "How can this book help me when I'm in that mood?" (e.g., I'm feeling tired -> Suggesting "Why We Sleep" to fix your sleep and understand why sleeping is essential).
Somehow, I'm happy because what I wanted to do becomes clear when you use the website (based on what you described, which is 100% correct). But that also means I could have worked my "marketing/copies" differently to reflect that more.