An excellent resource with very detailed discussions of bee morphology, behavior, and biology---from identification to genus, to in-depth coverage of (a surprisingly diverse variety of) nest architectures. Many helpful diagrams throughout. Very readable, even though largely written at a technical level. I find it a very interesting and helpful reference...only wish it included all of western (and not just northwestern) America! Nevertheless, I think much of the utility and information in this book probably applies to areas beyond the northwest---especially to adjacent areas.

And as a very nice additional bonus...this book can be freely downloaded off the internet! The portal page for links to the PDF's is here.