Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Mountain Biking Phoenix by Bruce Grubbs May Result in a Trip to the Emergency Ward

This publication is an earnest effort to provide a guide to Phoenix-area mountain biking trails. However, it contains inaccurate information and is woefully outdated. Many of the trails have either been encroached upon by new housing development or are presently closed to the public altogether (ie. Devils Hole in the Tonto National Forest). Descriptions of certain trails and the level of difficulty is also cavalier. It is irresponsible of Bruce Grubbs to author a publication on a sport as hazardous as mountain biking when he is clearly not an expert. There are some very good mtb trail guides for Phoenix out there; I'd recommend giving this one a miss.