The Pacific Crest Trail: A Hiker's Companion (Book) by Karen Berger and Daniel R. Smith

This guide begins where other guides leave off. While it gives some route info for non-through-hiker trips, plus resupply info for through-hikers, it excels at giving detailed location-specific info on what the hiker will encounter on the Pacific Crest Trail: points of interest, plants, animals, history, geology, trail conditions, seasonal info, etc. It's a true Companion. 321 pages.