Richie Millstone, the Firewater Dragon & the Gemstone Cities is the second book in a five book series. The series chronicles a continuous time travel adventure taken by a bunch of teenagers. The first book was Richie Millstone, the Firewater Dragon & the Platinum Water Crystal. The second book takes off where the first left off. Richie and his companions are trapped on a time machine ship lost far from home. They long to get back but are actually enjoying the adventure. The kids unwittingly get into all kinds of mischief and shenanigans as they try to get back home. In the first book, they visited Mars of the distant past, one point five billion years, to find a 1930's era civilization with feline ancestry. This book sees them visit even more exotic places while they fight to keep a powerful energy crystal out of the hands of a nefarious dragon and other evil persons. The crystal is rumored to have fallen from outer space and gotten its power by passing through a neutron star. Throughout the adventure, the kids learn lots of stuff about themselves and who they are destined to become as adults.