The author does provide a good overview of the brand and provides opinions on reliability and future appreciation of each model. The book covers mostly vintage bikes providing for each brief riding impressions and performance data.
Moto Guzzi is Italy's oldest motorcycle manufacturer still in business. Today they remain somewhat of a small volume producer with a limited US dealer network. Over the years they have produced some iconic masterpieces and some duds. Start here but do not take the author's opinion too religiously. Spend some time on the web in the specific Guzzi forums for a more complete picture.