In Dante's inferno those words were written on top of the hell's gate, and I think those should be in any Italian's wine book preface.
Italy is a very complicated wine country, we grow the highest number of grapes than any other, we have as many laws that identify a wine and as many exceptions. We have some grapes that are grown exclusively by just one producer like the Barbarossa, named after Frederick the first Emperor of Germany, in Emilia Romagna by Fattoria Paradiso.
The destiny of that grape was rewritten when in1955 Mario Pezzi discover it in a over 100 year old vineyard that was destined for the scrapers, now they are the only ones in the world growing Barbarossa. We have not-so-good DOCG's (the highest quality denomination reserved for wines like Barolo, Brunello and so on), and some excellent Vino da Tavola. Then you have the guys that follow the institutional guidelines, but they do not want to part of the institution itself, like Maculan and Anselmi in Veneto, who refuse the Soave DOC status, even though their wines meet the qualifications necessary. The same goes for Cascina Ebreo in Piemonte which makes a kick ass "Barolo," called "Torbido," but because of a vinification choice made by the house, it is categorized as Vino da Tavola.
In the belpaese every individual has his own way of doing things, and this is true with wine as well - learning about Italian wine involves a lot of drinking and studying. To this day I still come across new grapes that I've never heard of before; the wine business bloomed in the past 10 years and new wineries started to grow like mushrooms creating, if possible, even more confusion. For example, and just to make things a little bit more obsure we have a town in the south of Tuscany that is called Montepulciano were the Rosso and the Nobile di Montepulciano are produced, but we also have a grape that is called Montepulciano and is the most famous "Abruzzese" (from Abruzzo) grape. Sangiovese is called so in the Chianti area, but it changes its name to Brunello in Montalcino, Prugnolo in Montepulciano and Morellino in the Maremma area; Nebbiolo is also known as Chiavanesca in Valtellina.
With all of these essentially chaotic facts surrounding the study and enjoyment of Italian wine, it can be a very rigorous undertaking to build a substantial knowledge base - and even then, even after a lifetime of learning, there are still thousands of new things to know. At least we know that there is always something new to enjoy, right?