Weber Carburetors by Pat Braden
I really like this book for the great illustrations and detailed explanations. However, it doesn't have the usual VW carbs (DFAV/DFEV, although the DGAV is close). It only covers the: IMPE, DGAV, DFT, DCOE, and IDA3C. I have a DFEV on my Bug, so this book isn't directly useful. On top of that, even with all the detail, there aren't specific instructions about how to jet your carb. This book does contain jetting info for the Weber carbs that shipped at stock on many types of cars.