Of the three major mountain biking guides that cover Northern California the Falcon Guide is my favorite. Despite having fewer rides (67 versus the other two which each have a hundred) the trail information is presented in such a way to allow for efficient trail selection and detailed understanding of the trail's difficulty. Each ride is accompanied by a map depicting where in CA it is, a helpful schematic of the trail and an elevation profile of the ride. The books best feature is that each trail does not get a single difficulty score, but the elevation profile is broken up into sections that are each assigned a difficulty category (from 1 to 5). The rides tend to be on the intermediate to advanced side (though some good beginner single track is included) and there are no paved or easy rides (which the other two books include). To date I have found the trailhead directions and trail descriptions to be accurate and lively.