I've just got my paws on Wildflowers of the High Sierra and John Muir Trail by Elizabeth Wenk and let me tell you, it's good.
The quality of a wildflower book depends in part on a few things. First, your own level of botanical expertise, and second, where you are going to look for flowers compared to the range of area covered by the book. If you are a wildflower newbie, a book organized by flower color (as Wenk's new book is) will be easier to navigate than a book arranged by taxonomic families. If you are hiking just within Yosemite National Park, a book covering all of the Sierras or all of California will be overwhelming.
Therefore, my ringing endorsement of Wenk's new book is predicated on two things. First, it's a great book for someone who is new to flowers but holds value for readers with a bit more knowledge too. Second, and most importantly, it is mostly restricted to high elevation flowers between Yosemite and Mt. Whitney, and if you're hiking the John Muir Trail or scoping out flowers anywhere in that region, it's perfect. You won't have to flip through pages of flowers that only grow in lower elevations, because they aren't included in the book.
I really enjoy the written text in the book as it describes how the geology and other factors like sunlight exposure, soil depth, and rainfall affect which plants grow where. In addition to the photos and descriptions of each plant to help readers identify the flowers they see, these blurbs, which are scattered throughout the text, add to readers' ecological understanding of the area.
I also love that each entry includes the elevation and locations where the plant is found and notes how common each species is. It makes identifying plants so much easier if you distinguish between similar looking species because they grow at entirely separate altitudes or hundreds of miles apart.
Another small detail with a big impact is the handy table of conifers, telling how to distinguish one from another. It's a shame all plant identification books for the Sierras don't include this.
I've got only a few gripes about the book. First, she tells the family of each plant but gives only the Latin name and not the common name of the family. For amateur botanists who have not memorized all of their Latin family names, it would be much more convenient if "Onagraceae" was followed by "Evening Primrose Family." Also, in the text blurbs describing High Sierra ecology, the lists of species are always Latin names, and it would be helpful to include common names after them. It's true that common names are imprecise, but it would still be helpful to add the term "Yarrow" in parentheses after the Latin name "Achillea millefolium," and so on.
All in all, this book is a keeper, and I definitely plan to bring it with me on the John Muir Trail this summer. (For a backpacker, that is high praise, since every additional item added to your pack is that much additional weight you have to carry.) Compared to the three other Sierra wildflower books I've used to date, this one has the best combination of including the most flowers I expect I'll see while excluding those I don't and the most useful information to help identify each plant.