Thanks to the efforts of Dr. Reiner Smolinski and his team of scholars, the first volume (out of a planned ten volumes) of this massive commentary -- Genesis -- is finally due to be published by June 2010. It can be pre-ordered on Amazon here.
The format of this commentary is different than standard commentaries of his era. While Mather drew heavily on Matthew Poole's Synopsis Criticorum and corresponded with Matthew Henry directly, as noted on the Biblia Americana website:
In fact, even a cursory comparison between Mather's commentary and those of his peers reveals major differences in conceptualization, approach, and presentation of material. While both Henry and Poole follow the time-honored precedent of (1) Summary of chapter, (2) Reprint of each verse, (3) Analysis, commentary, and cross-references to related biblical passages, Mather's methodology abandons the traditional chapter summaries and reprinting of each verse. Instead, he devises (1) rhetorical questions for each annotation; (2) assumes a skeptical reader who would pounce on apparent contradictions in textual transmission, translation, and interpretation; (3) provides analyses and citations from opposing camps of the hermeneutical debate; (4) aims at reconciling new critical methods and scientific discoveries with conservative receptions of the bible.
It's importance in the field of Puritan exegesis should not be underestimated. The publisher writes:
Cotton Mather, one of the leading intellectuals of colonial America, has often been overshadowed by his younger Puritan contemporary, Jonathan Edwards. Now, however, the publication of this first edition of Mather's magnum opus in the area of biblical knowledge focuses fresh attention on early New England's second most prodigious intellect. Mather's commentary takes the form of questions and answers on the whole biblical canon. The edition, prepared by an international team of experts in early American studies, will consist of ten volumes published over the course of a decade. This first volume introduces the project and offers Mather's comments on Genesis. This work will be treasured by students of American church history, colonial-era Puritanism, Christian responses to the Enlightenment, American intellectual development, and the history of biblical interpretation. It is a must-have acquisition for research libraries covering these disciplines.