Hi Allan,
I don't know of any counterpart organisation to NSWA in Saskatchewan. There used to be something similar for the South Sask River basin but I can't find it right now.
Yes, the book is intended to be a guide for river travellers, including canoeists. It will certainly provide some useful information, as well as some historical context, however I think it is inadequate as a sole resource. I don't have my copy with me at the moment to make specific references, but I was disappointed with this book. I have used it while paddling the section from Borden bridge to Fort Carleton.
If I remember, I will have another look at the book and try to be more specific in my assessment.
As a side note, while I was working on my M.Sc. in Biology (Entomology) the folks putting this book together contacted me for information on the aquatic insects of the N Sask R. I couldn't answer their questions but was able to direct them toward a number of folks that were better qualified. For river-side reading, you may be interested in the book
Reading the River: A Traveller's Companion to the North Saskatchewan River, by Myrna Kostash with Duane Burton.
Reading the River is an anthology of writing relating to the North Saskatchewan River. It's not bad and certainly would be of interest to anyone that has interest in the area (and if you paddle it, you are probably interested in it). A lot of it is historical, with a bit of prehistorical accounts. There are writings from modern paddlers as well.
Cheers,
Bryan