Climber's Guide to Glacier National Park
By J. Gordon Edwards. Excellent guidebook--exhaustive and detailed, yet concise. Also the only guidebook, making it a must-buy. Make sure you buy the 1995 edition.
Kim and I hiked along the shore of St. Mary Lake, from Sun Point to Bering Falls, and then to St. Mary Falls and back again. My back was bugging me that day.