Some consider renowned photographer John Fielder a good Colorado book publisher, but the text for his books is generally written by other folks. His book on the Colorado Trail was a nice one. However, John Fielder is not native to Colorado.
John Fielder also did an excellent book about Colorado "then and now." It's pricey. $200, but it's worth it if you love Colorado or grew up here (like I did). He did a spectacular job of recleaying the historical scenes as they appear today. Text was again supplied by other writers, but he describes in his own words what it took to put the book together. A follow-up companion book was outstanding as well.
A history teacher/writer, Robert L. Brown wrote some greatg books about Colorado's history. They're rare and hard to find now. I have his book on the history of the Holy Cross Wilderness. If you stumble on any of his writings, you've found a treasure. His best known Colorado book is "Jeep Trails to Colorado Ghost Towns."