Another of Edogawa's "Boy Detectives Club" books, "怪奇四十面相" is, sadly, one of his poorest efforts, a novel that feels like an assignment instead of a work of love.
We, again, have the 'very scary' 20-faces guy as the big bad enemy of the story. In the best moment of the whole novel, he succeeds again in a daring escape from prison. This start is fun, full of energy and all of Edogawa's trademarks and seems to tease a very enjoyable story to come.
However, after that we get the constant tiki-taka between 'The Fiend with Twenty Faces' and Kobayashi-kun, one trying to outwit the other. In other cases this has offered some amazing moments and shown the incredible imagination of Edogawa, but here it feels old and stale, as if he just couldn't wait to get to the end and finish with the story. It still offers a couple of surprising plot developments, but in general, it is a weak effort, with little mystery or excitement.