It was an awesome adventure. The book is pretty accurate, except actual length is 16 miles.
You need permission at the takeout: Elkhead Ranch. You cannot drive to the put in. We snowmobiled to the put in. Sometimes they plow the road further than other times, but it may require a hike-in if no snowmobiles. Take overnight gear.
The first 4-5 miles are flat water [in California Park]. There are about 2-3 miles of stout V. The last 7-8 miles are continuous III-IV.
It has been super high. I would want to run it again when the gauge is going to peak around 1200cfs. We did the whole thing in one day, but we were lucky.