This is a good companion book to explore Yellowstone. But do keep in mind that the Tetons and Yellowstone NPs are so big, no guide will be extensive enough to cover all the parts of the parks and related activities. This lonely planet guide is a good way to get some pointers and help you out to plan your trip, giving you the highlights of the parks, but you will certainly need topo maps, or some hiking guides should you need to explore a particular area in depth. Nonetheless, this book is well written and does what it's supposed to do, i.e. orient you and give you an idea of what is out there for you to see. Should you need more specific info, just use the guide as a starting point and google up the rest (or buy another more specific books that pertains to driving or hiking or whatever you want to do in these parks).