I picked up this book because I saw it mentioned as an example of the concept that "Hell is locked from the inside." That is, if God is the source of all good, then by separating yourself from God, your existence can have nothing good in it, and that's Hell. You can escape anytime by reconnecting with God.

Lewis explores this idea by imagining himself being taken on a journey from Hell (envisioned as a dreary, lonely, mostly-empty town in perpetual twilight) to the outskirts of Heaven. Here the "ghosts" of those in Hell are met by people they knew in life, who try to persuade them to enter Heaven instead of turning back. This is very much inspired by Dante, and like Dante, Lewis gets a guide: the Scottish fantasy author George MacDonald, who I'd never heard of, but apparently he was a great influence on Lewis. (Has anyone read his stuff?)

So, why would the dead turn back? Well, because it turns out the hard part of getting into Heaven is letting go of all the damaging patterns that made you miserable in life: Abusively controlling people and calling it love. Feeling big by making others feel small. Manipulating loved ones because you're scared they'll leave you. None of this has any place in Heaven, but most of the ghosts Lewis meets are so entrenched in it, blustering in pride or cowering in terror behind their emotional walls, that they'd rather go back to Hell than admit there's a better way.

Lewis keenly observes the lies people tell themselves to justify their own self-destructive behavior, and it's startling how little has changed in 80 years! Some of the ways these characters talk are chillingly familiar. Though I don't share the religious side of Lewis's worldview, we're certainly in close agreement in our understanding of how people lock themselves in their own personal hell on Earth.

The book is short but impactful. Lewis had a gift for viscerally expressing what his faith felt like to him, which is something I find valuable as someone who has never experienced religious faith. Part of why I read is to better understand what it's like in other people's heads, and this book did that for me.

(Oh, and I'm not being snarky by tagging this as fantasy. He calls it fantasy in the introduction! He makes it clear that he's writing imaginatively and not presuming to describe what the afterlife is actually like, because he can't know that. Well, I mean, I guess he knows now...)