There's murder, too, of course, including murder in a completely dark restaurant where the servers are blind and no one can see a thing. The killing is connected to a skull that Monk finds in the catacombs, not that there aren't thousands of other skulls there. You'll have to read the book to find out more.
And of course there's plenty of Monk's quirkiness, which I continue to find amusing. This is where the title of the book is somewhat misleading because before it's over, Monk has found something approaching pure happiness driving a motocrotte. Again, you'll have to read it for yourself, which is something I recommend the next time you need a good laugh, an entertaining mystery, and a tour of the Paris underground all for the same price.