The verdict: great stuff. I find it surprising that it never appeared on a syllabus of any class I took (or received mention). It is a big book in the sense that it is long (626 pages in my edition), ambitious in its representation of characters across many social and economic strata, verbally compelling (i.e., intense, poetic descriptions), and detailed in its descriptions of physical and interior worlds. Mailer captures hard men not by giving them inscrutable exteriors, but by sinking deep into their thoughts, fears, half-recognitions, contradictions, and so on. Interiority, I suppose, is associated with sentimentality in some ways, as well as slow action. Not the case here, though at times the action is slowed in an intense way to represent the agony of the soldiers.
Some of Mailer's characterizations seem dated and clichéd -- for instance, the "natural" man Wilson, who has a whiff of Erskine Caldwell about him. Still, this book was one of my most memorable reads in some time. I'm going to try to keep Executioner's Song on my radar, and I may try to read something by James Jones soon (maybe The Thin Red Line).