The book is subtitled "A provocative view of the way money works". It's in the same format as the other Fragile Earth books; a collection of numerous mini-essays around a single theme. I don't think the format worked that well since money is quite a complex issue and there are many interconnected concepts that need more indepth explanation.
It's a good "taster" book for covering a wide range of ideas and insanities. For example, the concept of GDP is badly flawed as an economic measure and a way of measuring progress. Money that loses value over time to encourage economic activity. The guaranteed citizens' income. There is more debt outstanding than there is money to pay it off. About one third of all global wealth is held offshore. The problems and history of interest (usury). Micro-credit. The Tobin Tax. And much more.
The section on DIY money was particularly interesting. He creates an arguement that we should generally have many more currencies rather than fewer. Lots of interesting examples of how effective this can be (e.g. LETS). One great illustration was the Brazillian city of Curitiba which issued points for recycling their rubbish. This was enthusiastically collected by street children as they could spend the points on off-peak bus rides. It's a great solution since you get a clean city just by using spare bus capacity.
The book begins with this fantastic speech by Guaicaipuro Cuatemoc to European heads of state. Well worth reading it as it eloquently claims a 500 year old debt for the loan of 185,000 kilos of gold and 16,000,000 kilos of silver - with interest!