Here is the problem with your very valid question. People who
only carried
Brierley will tell you that the
only guidebook to carry is
Brierley. People who
only carried Village to Village will tell you that the
only guidebook to carry is Village to Village. And people who
did not carry a guidebook will tell you that you don't need to carry one. Everyone seems to be determined to justify their choices.
On my last Camino, I carried
three guidebooks (and yes I know this has many on this Forum clutching their pearls and complaining of the vapors)
.
I carried
Brierley, Village to Village, and the exquisite German guidebook. If you don't speak German, then I'd recommend Village to Village over
Brierley. And yes, a guidebook is not necessary to find the Camino (I truly get that following the yellow arrows is simple). And yes, a guidebook is not necessary to locate places to stay (I truly get you can download applications for your smart phone that lists accommodations in each village).
However, if you want to take a 15 minute break and sit in front of a church and read about it's rich history and why it's significant to the Camino, you are going to need carry a good guidebook. No current app that I know of does that for you.
Guidebooks are also great for giving you the pros and cons of alternate routes. No app that I know of helps you decide whether to go left or right when you come to a fork in the path.