The front half dragged quite a bit, however it was very fascinating to listen too. The dialogue was a little bit hard to follow, partly due to the accents the narrator used, and also because the audiobook swaps between reading the dialogue like you would in a book (he said this, she said that, etc...) and other times would adopt more of a playwright's method of denoting dialogue. I do like how it all went down in the end tho, and I appreciate that Lord Whimsy isn't like, a super genius, he himself acknowledges that he's just a rich dude with a funky hobby that he picked up from reading too many mysteries as a kid. The brief little commentary on PTSD and it's many forms after WWI was also a nice touch of depth. Unfortunately the audiobook I checked while came from a downloaded copy of a CD, and disc 4 must've been scratched cuz I missed a little bit at the end of the disc. 
While it was overall fun to read, and I still want to read Strong Poison due to seeing the play adaptation in college, I probably won't go out of my way to read every book in the series.