Reddit mentions of Ultimate Navigation Manual

The Ultimate Navigation Manual is one of the best reference books to any skill that I have ever encountered, very clearly written with tons of clear photographs and illustrations to help depict concepts. I highly recommend it to anyone that might have need of navigation skills.

Skurka's book is good (likely the best way to get up to speed on gear), and his blog is excellent as well.

Other books I like:

• Lighten Up!: A Complete Handbook For Light And Ultralight Backpacking (Falcon Guide) (A bit old, but still a classic and the other "Allen and Mike's" books are also good.
  
• Lyle Brotherton's Ultimate Navigation Manual
  
• NOLS Wilderness Medicine (Be careful; the Kindle instance is actually an old version.)
  
  For current information, these subreddits and sites like BackpackingLight will get you up to speed.