For anyone interested in Northwest Native Plants, this is an essential reference. Arthur Lee Jacobsen's "Wild Plants of Greater Seattle" is another useful book, although not as detailed. "Vascular plants of the Pacific Northwest", by Charles Leo Hitchcock, in 7 volumes for $300.00, is much more detailed but not as handy. I have used my "Pojar" so much that I wore it out and had to get a second copy. I found it useful when I was just beginning to learn about native plants, and now that I can identify over 200 species on sight, I still use it to learn about ethnobotany, which plants are edible, and where to plant them in my garden.
Another reviewer complained that the book does not list common names in the index. This is just plain wrong. You can look up plants in the index by common name or scientific name, or you can browse through the photos until you get a match. You can also use the keys, which is the best way to learn about the relationship of one species to another, but I'm usually too lazy to work through the process. The way the plants are grouped, it's easy to narrow it down and find your plant.
My one complaint about the book is that it is sometimes difficult to pin down whether or not a particular plant is actually a native. This is usually implied, especially when they tell how indigenous peoples used the plants in everday life, but I wish the plants were clearly marked Native and Non-Native.