Are Gran Class trains included in the Japan Rail Pass ?

Only the basic fare is covered with your Japan Rail Pass, so if you'd like to use the GranClass car of the Tohoku Shinkansen, Hokkaido Shinkansen, Joetsu Shinkansen and Hokuriku Shinkansen, you must pay the limited express charge plus the GranClass car surcharge.

It is not something that you can pre-book, so you must enquire directly at the JR ticket office (Midori no Madoguchi).