This little snuff box belonged to Thomas Coke (1747-1814). Coke was the first Methodist bishop of the Episcopal Church in the Americas and is sometimes referred to as the Father of Methodist Missions.
Snuff is a form of smokeless tobacco which is made from ground tobacco leaves. It is inhaled (or 'snuffed'). Snuff originated in the Americas but was popular in Europe from the 1600s. It may be that Coke acquired the habit for snuff whilst living in America in the 1780s. Fittingly, the snuff box is in the shape of a book.