Yeah okay, it's a YA book, don't judge it too harshly, but the series is really starting to feel a bit like a one-trick pony. Lemoncello is rich and fabulous and holds crazy library-based contests and games, which kids run around solving. It's nice kids are being encouraged to use the library and read books. This book had a bit of a theme about how it's okay to fail. But there wasn't really anything new here that wasn't in the first books, and the general set up of the plot was pretty sketchy on realism. (Lemoncello's rivals accuse him of ideas theft and set up some extremely thin bits of evidence, like editing his wikipedia page. On the basis of this, Lemoncello is discredited, the library is removed from his control by the mayor, and given to his rivals? Lemoncello meanwhile refuses to raise a finger to defend himself or to have his lawyers do the same, and instead leaves it to the kids? None of it really made any sense.)

Meh, I mean if your kids are enjoying it then let them read more, but I'd suggest also buying them a collection of Sherlock Holmes short stories. which are probably better reading for them overall if they like puzzles.