Two books deal with early roads in depth. In addition, nearly all of the individual town histories have chapters on roads.
"On The Road North of Boston" by Donna-Belle Garvin and James Garvin discusses the taverns and travel conditions as well as providing a great deal of information on the roads and turnpikes.
"The Turnpikes of New England" by Fredric J. Wood contains information on the New Hampshire turnpikes, as well as other New England states. It's particularly useful in that it makes clear which turnpikes, although chartered, were never actually built.
An informative article from Outlook Magazine:
Turnpikes, Stage Coaches and the White Mountain Express: Transportation in the White Mountains
by R. Stuart Wallace (click above to read full text)
The Littleton Turnpike from the end of the 10th New Hampshire to the Connecticut River in Littleton.
Mount Washington Turnpike from the Fabyan House to the Base Station of the Cog Railroad.
The Carriage Road (now the Auto Road) up Mt. Washington. This is the only private road still collecting tolls in the state.
The Coos Turnpike