Chronicles of the City-States: Amandine's Invisibility Cloak

This is the second book in the City-State series, originally titled The Cloak of Invisibility. Amandine unexpectedly comes into possession of a priceless treasure: a cloak of invisibility. But the cloak has one fatal flaw: it only works while he holds his breath. Determined to stay invisible for longer, he begins training himself to hold his breath, setting off a series of hilarious mishaps...