I'm not sure where you are, so this may be too far. However, my son and I had a wonderful time riding some rides near Santa Fe, NM, this summer, which we got from a book called, Mountain Biking in Northern New Mexico: Historical and Natural History Rides. I think the author is Craig Martin.

Lava flows and turquoise mines and ghost towns and the Camino Real. Not just cutting down single track, but rides with destinations.

Karen