I'm more curious how Publisher's Weekly defines "sales" in this era of subscription plans (e.g. Kindle Unlimited).

Some of this probably isn't just "AI" but the quantified/journaled lifestyle trends. Do Oura rings and Apple watches impact self help as much as basic health questions on Google and routine doctor visits?

It feels more like a broader information abundance and a more educated consumer base that started over at least a decade ago. AI's impact is hard to measure since it's just the hot feature resting atop existing tech. It certainly did none of the heavy lifting to nudge people this direction.