I didn't like Alan Bradley's The Weed That Strings the Hangman's Bag nearly as much as the first book in the series, The Sweetness at the Bottom of the Pie. Although Readers' Advisors are supposed to look for what in a book will be appealing to readers, all I can do now is take the opposite approach and try to identify what I didn't like about it.
I just felt detached from the book. There's no suspense in it; the first was by no means suspenseful, but the second didn't thrill me in the least. I read for characters, and I already know Flavia de Luce, the young detective girl. She didn't develop in a significant way, and her character as an anomalous curiosity has worn off.
Much of the story line was relayed via storytelling from characters' mouths. This is not to say there is not description, but the writing did not feel as lush and evocative to me as the first book. Details relate to World War II, puppeteering, chemistry, the vicarage. The pace is leisurely. The language is fun and witty, and the tone would be quite dark were it not for Flavia's childhood perspective.