Corinna and Daniel must follow a breadcrumb trail of nursery rhyme clues left by a crazy homeless former accountant who knows the location of some missing bearer bonds left by a bullied intern in a phone booth. The fact that none of the clues and been thrown or blown away after being tucked, sometimes days before, in public places was more unbelievable to me than the conceit that some one would actually leave them in the first place. One requires suspension of disbelief, the other suspension of the laws of nature (especially given the repeated storms throughout the book).
Kerry Greenwood is a touch under 60. The age of her protagonist is unstated but she seems to be vaguely "middle aged" given her described career trajectory. The tone of the series, however, is increasingly old-lady-ish. Oh, those kids with their incomprehensible text messaging abbreviations! And their clubbing and their inability to quote 18th-century poetry! I don't think most old people go around dropping classical allusions into their conversation, either. That's always been the province of a small educated elite.
And if you're going to be snobby please, PLEASE stop using the word "YUM" every other page. The descriptions already make the food sound delicious, you don't need to keep stating "Yum." Especially as an independent sentence.