Fretting hand question

I was taught to hold the mandolin in my fretting hand with the mandolin resting on the ball of my hand where the index finger meets the palm. I then support the other side of the neck with my thumb. I purchased a book recently that said to hold the mandolin in a kind of... pincer grip? Basically with your thumb on the back of the neck of the mandolin and the rest of your hand more free floating. Is there an explicitly proper way to hold your mandolin, or does it matter? Because if the book is right, I've gotta relearn how to hold my mando after three years. Dang.

The book is wrong. But, please note that you don't hold, support etc. the mandolin. The fretting hand is there to stop the strings. The mandolin rests on your knee or in your shoulder strap -- check out Mike Marshall's d'Addario video on Youtube.

Secure the mandolin in place and then bring your hand to the neck and start playing. Your hand will land in approximately the position you describe. E.g., the thumb will land on the side of the neck and possibly trail behind on moving up the neck. Barreing may cause the thumb to slide in under the neck. but don't force it anywhere.