This note contains spoilers for the book.

I always see the title as a pun on habeas corpus. I do not believe this is an accident; there are at least two references in the book.

This is Harriet's book, though Peter shows up fairly early. She hasn't invited him, though; and he's a little hurt that he had to hear about this excellent little corpse from Salcomb Hardy.

This take place after Peter and Harriet have met, and rather before Gaudy Night. Things like their very first dance take place.

It's a complicated plot, involving people having spare identities handy, and running around the country as various people. Too complicated, I think; not so reasonable.

And, in the end, it's left ambiguous if the case will ever be brought to trial, even though they think they know for sure what happened.