I got my copy in the mail a few days ago, and had been trying to read it cover to cover before commenting, but decided it won't wait.
This field guide is truly ground-breaking (no pun intended), with two types of keys, plus thorough explanations of the characteristics used to identify genera, species groups, and individual species of New England ants. The guide includes all the known species of the six-state region, plus some found in adjacent parts of adjacent states and Canadian provinces. It would serve well for identifying almost all the ants of northeastern USA and southeastern Canada, especially those of the Great Lakes Region.
A novel feature of this guide is the inclusion of not yet formally described or named species, based on the authors' consultations with taxonomists such as myself, Andre Francoeur, and Stefan Cover who are working on revisions of the genera that contain these species. Each is given a code name, or uses the qualifier "cf." before the name of a closely related, described species.
The book is not without its flaws, including some presumed publisher or author errors, but none are "fatal", and there is a lot of blank space on most of the species pages, perhaps left intentionally, so that later printings can include corrected, expanded, and updated information. My main problems with the book regard two sorts of illustrations:
1) the low-resolution and rather dark rendition of the stacked-image photographs and
2) the sometimes crude and/or inaccurate drawings and colors in the matrix keys.