You know a movie is great when it leaves you hyperaware of your surroundings long after you walk out the theatre. Your senses heighten, and the world you return to feels like an alternate universe. A great book is no different in delivering the same impact between chapters.
And it is this great book that inspired the reverent Hayao Miyazaki to dedicate one more animated film to his grandson. Naturally, a story that can pull the Studio Ghibli maestro out of retirement is enough to pique anyone's curiosity.
Background
Originally the final feature of serial publication Nihon Shosan Bunko Bunko (A Library for Young Japanese Nationals), it was written by Yūzō Yamamoto, who was unable to complete it due to a severe illness. He then appointed editor Genzaburo Yoshino to take over, and it was eventually published it as a book in 1937.
Fun Fact: It was initially intended as an ethics textbook rather than literary fiction. Fun Fact II: Yoshino wrote it after release from prison, following his arrest for attending political meetings with socialists.
The story
Off the bat, keywords would be Coming-of-Age, Introspective and—god forbid—Poignant. The good news is, the book is exactly these overused novel descriptors, but in a light and uplifting way. You get a look at a segment in fifteen-year-old Copper's life, and his reflections guided by the wisdoms of his uncle.
The narration opens by addressing you, the reader, the way children cartoons do, and this voice is used moderately through the book. It engages without making you feel patronised, staying relevant to older audiences despite it being aimed at the young.

Themes
Though Copper sounds relatively naive for his age, we bear in mind that this was a much simpler time that predates the Internet. Heck, it even predates the Second World War. Still, there's nothing facile about it. Chapter One already mentions Copernican heliocentrism (google that why don't you) and ties the astronomical term with the human realisation akin to John Koenig's fictional word Sonder.
Alongside a fair bit of history lessons, it acknowledges universally relatable emotions, as well as the social class gap; a subject still enduring the times (see 2019's Parasite). All this against a backdrop of picturesque text that effortlessly imprints the visual mind.
Similar books
In the foreword, Neil Gaiman draws the parallel with Herman Melville's Moby-Dick. Gaiman, who has worked on the English script of Miyazaki's Princess Mononoke, makes the comparison for its opposing elements between Copper's perspective and his uncle's.
I personally liken it to Jostein Gaarder's Sophie's World for that dual view, and Tetsuko Kuroyanagi's Totto-Chan in execution. It's not an easy feat to write from a child's point of view convincingly, more impressive then for it to speak straight to the child's heart of every adult.
It's hard to imagine how the book's depth and insight would be conveyed in the anime in entirety, but if anyone to entrust that task to, we would certainly be excited for it to be Hayao Miyazaki.
And what about you? What will you create? You take many things from the world, but I wonder what you will give back in return?
—an excerpt of How Do You Live?