Hi pals, just wanted to recommend something that isn't explicitly a dharma book, but its themes cover the Dark Night and morality really well. It's called "Everything Matters!" by Ron Currie Jr. It's a good allegory of what to do (and not do) when you're sifting through a lot of darkness and how it's tempting to let it bleed out and affect the people you love (Spoiler: Don't).

I am at the tail end of the autobiographical section of MCTB2 and some lines brought that book to mind.

The author gets compared to Kurt Vonnegut a lot, so if that's your thing maybe that will entice you?

Also recommended in that same vein: A Wizard of Earthsea

A Man’s Search for Meaning

A lot of good Russian and Eastern Block classics too numerous to mention, but Crime and Punishment is an obvious one.

It's more on the "coping with massive changes in your subjective experience" side than on the Dark Night or morality side, but I've really enjoyed reading A Succession of Bad Days by Graydon Saunders.