I bought a copy of this book on Sunday, at Metzger's Maps, for $25. Which works out to learning about 3 routes per $1; seems like a good deal. It turns out Amazon has the book for $15. The guy who wrote the book (and a few others) has a cycling blog, and publishes photos from some of the routes online.
Some of the routes are pretty obvious if you look at a map, or talk to other cyclists. I've already done a few of them: the Leavenworth/Plain loop (the book omits Lake Wenatchee, a must see), Icicle Creek, Steven's Pass or Skykomish to Leavenworth, and the Mount Baker Climb. All of these are fantastic rides, and I hope that means the rest will be, too. I would have done a few of the other 70 or so rides without learning about them through the book, but most of them look like ones I wouldn't have stumbled on. Here are more routes the guy recommends.
I'll bump this thread after I've had a chance to ride some of the routes I didn't already know about. Until then, two things stand out: a few of the rides the guy suggests have narrower shoulders or more traffic than the ride description seems to let on, like new Blewett Pass, and Route 2 approaching Steven's Pass from Skykomish, which made me especially nervous. While there are a few island rides, most of these are in the mountains. Not just the Cascades, either, there are a few rides in the Blue Mountains, one up Spokane Mtn, and several in the Okanogan.
I've had a hard time finding good routes to ride. I usually manage to, but it takes a lot of time and energy, researching places I've never been, or haven't been to in years. I ride mostly for the scenery, and tend to do solo rides. This is the third guide book I have for road cycling - the other two are Puget Sound, extending as far out as Granite Falls. You can see why I'd want a book like this. If you find yourself looking for new places to ride, and enjoy climbing, you should check this one out.