There certainly are not near the numbers of fish much above Steamboat as there are below, but fish can sometimes be found clear up to Soda Springs. I generally struggle to find fish in the upper river, just like last weekend, but one time 6 or 7 years ago I landed 2 fish in 2 casts, so one can get lucky. There is a lot less holding water above Steamboat, and Steamboat Creek is the major spawning tributary, so you won't find big numbers of fish up there.
New Spey, don't put too much stock in the Doc Crawford book. I picked it up at a bargain table some years ago, for the maps, but other than that, it's not too useful IMO. A much better read--as well as useful fishing info, especially if you read between the lines--is "A River Seen Right: A Fly Fisherman's North Umpqua" by Michael Baughman, with photographs by Dan Callaghan. I have a review of it on Amazon:
I did fish some below Steamboat last weekend, but it was quite crowded, and didn't help my results. The places I fished were places that have been very productive for me the last few years, but they didn't yield a single strike. I've made such a habit of avoiding the Camp Water that I forget to even look and see if it's not crowded. Having become enamored with the dry fly the past couple years, I'm sure I should spend time fishing Kitchen, for example, but I prefer uncrowded conditions when I fish, even if it means I catch less, so I almost always fish up or downstream a ways.