Author here!

To be fair, there is no particular backstory. I picked a hermit crab as the book logo since crabs are strongly associated with Rust due to Ferris, Rust's mascot. I then landed on that style (and the skull) because they looked sick and distinctive. The cover images of many technical books are incredibly dull these days.

Rust community members are known Rustaceans which is a play on the word crustacean. Crabs are a well-known crustacean. Crab in a human skull is a visual metaphor for learning Rust.

I do not know the story, but I remembered the book because of that, and now after having mentioned it here, I just bought it.

So my n=1 study indicates it was a successful design. :)

I got a Hamlet vibe from it when I picked the book up when it originally released. It could just be because it looks pretty sick though