Have you checked out Addicted Fishing on YouTube? They are based out of WA but fish the Columbia, etc. and have a wealth of knowledge. If you want to learn how to tie a steelhead rig and fish it, that's a really great place to start.
EDIT: I also own both books
@troutdude recommended and I recommend buying both of those as well. In addition, you can't go wrong with anything from
Amato Books. I refer to the
Oregon River Guide all the time still. It has fewer spots than "Fishing in Oregon" but the spots it does cover it does so in great detail, including technique, time of year, average counts, etc.