Soggy Sneakers is THE guidebook for those of us living Oregon... it does cover several of the close Washington Rivers, but not a ton. Paddling Oregon is another good one. That said, if you are going to get one, get SS. FYI, SS is written by Pete Giordano, who is one of the featured paddlers on Oregon Kayaking... he owns and runs Blue Sky Rafting up here and is a great guy. I think he might be in the process of doing an update... we paddled together last weekend and were noting that many of our rivers changed in the floods we had a couple of years back.
As for Washington, there are 2 books... Guide to Rivers of Washington is geared more towards kayakers... the other (can't remember the name) is written by a rafter... it is good in it's own regard and has some pretty good diagrams of river hazards. That said, they are both pretty out of date and I've noticed some of the information they present is not super accurate... best thing is to look at both.
In any event, welcome to the PacNW!