It had a green cover, I think. I'm sure it was somewhere here on itch.io I came across it. When I search, I can only find a PICO-8 zine.

Not found it? I would read it. Roguelike is interesting genre for me.

Found it! Sadly, it looks like the itch page was pulled. Here's a backup of the original sales page:
https://web.archive.org/web/20170917043604/https://rodneylives.itch.io/atplay

But I found a version for sale here:

https://www.routledge.com/Exploring-Roguelike-Games/Harris/p/book/9780367482596