Mark Twain does two things
1) writes meandering yarns.
2) disguises what he’s writing as a meandering yarn.
Unfortunately this is the former and I have to really be in the mood for the former. Secondly it is a jolly-natured send-up of Sherlock Holmes stories, which would be great if anything Twain wrote even remotely approached the intelligence of a Sherlock Holmes story. As is, we have to settle for the literary equivalent of raspberry blowing.
The ‘double-barrelled’ element is that the story hinges on two interlocking tales of revenge. It’s not particularly interesting, and if you stop for a minute to think of what’s actually happening in one – a woman brings up her son to be a tool of her revenge on the man who sexually assaulted her, the boy’s father – it loses even the affable charm that usually saves Twain’s duller work.
Read something else. This one’s easily missed.