Haven't hiked it yet, but this book gives the most comprehensive look at the JMC, both North bound and South bound. The reason I bought this book was because it gave details on both directions. It doesn't give you a daily guide because it knows that each person will have his or her own pace. The only thing I didn't like is that it spends too much time describing fauna and not the trail.
It is also meant to be a trail companion and to be read on the trail. Why? If I'm on the trail why do I need to read about it? Some of the detail is useless unless you are right there looking at it. However, the description of the trail and the maps are valuable (I especially like the elevation maps given for each section)
It also gives very important information on how to get to the trail, permits and where and when to get them along with some great mileage charts.

Great book for on the trail, a good book for preparation.

The previous version of this book was, I believe, considered to be the definitive JMT book, and this new version must be also. In it are all the details anyone attempting or thinking of attempting the John Muir Trail will need to know; what clothes to take, which food is appropriate, permits needed, bear information, a guide to the flowers of the area, history of the trail, geology, directions and even maps and a list of possible campsites. In fact, details are the thing about this book - it's ram-jam with them, and I couldn't think of any detail that I'd like to know that wasn't covered (I've hiked the trail once)!

This is a guidebook for those intending to hike the trail, not an account of someone's experiences, but even so it must get even the most couchy potato interested in getting out and walking! I did find the referencing of the sections and maps a little confusing, but it's a small point. And it might be a little large too, so I'd probably elect to photocopy parts of it, or rip out sections to take on the trail.