I’m not sure, overall.
As a kid, it was Mrs. Brisby and the Rats of NIMH. As a teen, it was The Restaurant at the End of the Universe. In my twenties, it was probably A Brief History of Time, The Art of Human-Computer Interface Design, or Steven Levy’s Hackers. In my thirties? Um, maybe… From Hell. Or Promethea. Or Persepolis. Or Adrian Tomine’s Summer Blonde. Or Craig Thompson’s Blankets. Today, it’s mostly a dead heat between Stephen Greenblatt’s The Swerve, Umberto Eco’s The Name of the Rose, and Liu Cixin’s The Three-Body Problem.