The NOLS book is great. Like any of the texts on the subject though, it is especially good if you take one of their courses. That's the thing about Wilderness First Aid. You really want to practice, and be put into some uncomfortable situations, and see how you are supposed to handle things.
The books make it seem so, I don't know, academic? Instead, at a NOLS course, or a SOLO class, you might be hiking on your weekend training, and you'll come across someone lying at the base of a nasty rock ledge, with a bloody mess about them. You'll be improvising a lot, managing the safety of the scene, learning how to lead the other folks around you to support the rescue, stabilization, transport, etc. It's well worth the weekend for WFA, or much more than a weekend for WFR or WEMT. If you're leading groups in the wild, you really owe it to them to have the training, even if it's not "required".
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- Ron