Amory was our driver / guide for a 2.5 hour tour in the mid-afternoon. He was friendly, knowledgeable about the park and the Navajo culture and traditions and as stated by another reviewer, he knew more about my Android phone camera than I do!!
This was our third trip to Monument Valley. 20+ years ago we took an extended tour with a Navajo guide and were able to see parts of the park that are restricted. That is true with the 2.5 hour tour with Tinhorn Tours. We saw things we had never seen before on the previous 2 trips. Our 2nd trip we did the self-guided, drive your own vehicle - I would only recommend that for a high clearance SUV or similar vehicle. Although there are signs with the names of rock formations, you simply don't get as much knowledge as with a Navajo guide. Amory was the BEST! Because it was quite cool, we had a fully enclosed vehicle so were very comfortable and a private tour since it was not peak season. It was definitely worth the money and I'd highly recommend. And we even got the added service of Amory meeting us the next morning to return the binoculars we left in his vehicle! Above and beyond!