The problem with funny books is that they often forget silly things like characters or plot. 
 In Whispers under ground the murder mystery is basically non-existent and mainly focused on discovering who is the owner of a earthenware warehouse. Long, boring, inconsequential interviews all dance around this gripping dilemma. If you have already started yawning, try imagining this stretched for 300 hundred pages... 
 As for the characters, the only one with a hint of personality is the protagonist and, let me say it, he his basically a douche bag. Yes, sometimes he is funny but most of the time you just want to yell at him: "Grow the fuck up!" 
 I really don't know how so may readers managed to compare this series to Harry Potter: in the hands of Peter Ackroyd even London loses much of its charm and the few magical traits of the story are uninteresting and boring. 
 I'm not saying that the book didn't get some sincere laugh out of me, it did, but mainly it dragged itself forward between flat dialogues, a bunch of secondary characters that miserably fail to be interesting and one of the most boring murder investigations seen in literature. I probably won't repeat the experience again.