A couple of "Critical Editions" considered, for those of a scholarly bent. (11th in the search for the ideal edition for an MDM)
In the Wikipedia article entitled Textual criticism, a "critical edition" is explained as "a text most closely approximating the original, which is accompanied by an apparatus criticus (or critical apparatus) that presents: the evidence that the editor considered [...], the editor's analysis of that evidence [...], and a record of rejected variants."
By definition then, a critical edition is going to come burdened with a boatload of what, to the marathoner, are extranea. This is content of no use at an MDM; that will provide only distractions and unwelcome weight. (Recall the criteria for an ideal MDM tome.) Still, you see these editions at the MDM (bought for some Literature course, probably), so a quick review might be of some value to someone out there.
The Norton Critical Edition, Second Edition was published in 1999 to celebrate the 150th anniversary of M-D's appearance. It presents the Northwestern-Newberry text, and is edited by two of the scholars whose research produced that text: Hershel Parker and Harrison Hayford. Although some readers may prefer the First Edition of this title, Parker and Hayford's Preface explains that the Second Edition reflects their study of the "Augusta Papers" and other caches of family letters that were discovered after the First Edition. The Preface also explains that "Note on the Text" and "Historical Note," detailing the editorial decisions of Parker and Hayford, were left out of this Second Edition because they are included in the Northwestern-Newberry edition. Perhaps to compensate for the excision of those notes, this edition has footnotes up the wazoo. Melville's own footnotes are mixed in with those of the editors, with "[Melville's note]" appended. (Not ideal for the marathon, if you're at the podium and choose to read M-D's footnotes.)
In addition to the "copious footnotes" are maps; a glossary; an illustrated discussion of whalecraft; contemporaneous engravings, articles, letters, essays, and reviews; 20th-century essays from William Faulkner to Camille Paglia; and a nice piece by Hershel Parker himself, discussing Melville's lifelong difficulties with lucre.
The specs: 5.5" x 9.3" x 1", 768 pages, 22.5 ounces. There are almost as many pages of addenda (310) as primary text (427). Chapter title headings on the recto pages; chapter number headings on the verso pages. The paper is rather thin, smooth, and white with moderate show-through. It has a sturdy glued binding and is "floppy"—no problem lying open. There's no mention of acid-free paper. A note on the copyright page states that the text is set in Fairfield Medium, display is set in Bernhard Modern. The typeface isn't distracting, but smallish for old me (the footnotes are a blur). See the Typeface Tally for a sample.
The other edition considered here is the Longman Critical Edition (2007), currently out-of-print, but available on Amazon. This edition aims to improve the Northwestern-Newberry text by adding "certain corrections and revisions derived from the British edition as well as changes made by the editors." I'm no Melville scholar, but I'd be interested to hear Hershel Parker's take on this effort.
Wyn Kelley read from this edition for her turn at the podium. Can we take that as a tacit endorsement? Probably not. Maybe she'll suffer an interview on the subject at MDM16.
This edition also has copious footnotes, that are set apart from Melville's footnotes to avoid confusion. Text that differs between the original American and British editions is set in bold grey type. If the difference merits explanation, a "Revision Narrative" appears at the foot of the page.
In addition to the footnotes, there are seventy pages of Explanatory Notes following the text. Then thirty-nine pages of further Revision Narratives, notes on other changes, and a bibliography of Melville's sources. The edition concludes with maps, whaleship illustrations, and a nautical glossary. If you want to get into the nitty-gritty of unravelling M-D as Melville intended it, this book's for you.
The specs: 6" x 9" x 1", 660 pages, 28.5 ounces (on the heavy side). Chapter title headings on the recto pages; chapter number headings on the verso pages; each chapter begins on a new page. The paper is smooth and bright white, a bit more substantial than the Norton, with a bit less show-through. It, too, has a sturdy glued binding and flops open easily. There's a note on the copyright page, next to the IBSN: "(alk. paper)," meaning alkaline (or acid-free) paper. The type is about ten percent larger than the Norton; the text's typeface looks identical. See the Typeface Tally for a sample.