I just finished Against The Day and, frankly, I'm not sure what to make of it.
It's impossible to avoid comparing it to Gravity's Rainbow. Both works have a drifting, disjointed quality to them. They feel like Mr. Pynchon sewed them together from scraps and ideas he'd written down in notebooks over the course of his career.
At least this time I don't feel like the butt of an elaborate prank. Where I went to college we had this joke about two horses, the point of which was to draw the telling thereof out as long as possible, only to deliver a deliberately lame punchline. Finishing Gravity's Rainbow, finally finding out what was up with with the rocket and all that, I found it easy to imagine Mr. Pynchon sitting in a leather chair somewhere and quietly chuckling to himself. Dammit, you post-modern ass-clown, that's 800 pages of my life I want back.
Anyway, this time at least he's not guilty of that. There's an actual plot, though when you strip it down to its bear essentials its actually pretty banal. But then there's all this... random shit. There's just no other way to characterize some of the tangents in the book.
For instance, at one point in the book we find ourselves suddenly accompanying some artic explorers. In a sequence that's best described as "HP Lovecraft meets The Thing" these explorers dig up a nameless horror from under the ice and transport it to some large city (maybe New York?), at which point it escapes from the ship and causes a general holocaust. Then the story meanders on to some other locale, never to return to the horrible beastie and the ruined city. Allegory? Fever dream? Fucking-random-tangent-because-I'm-Thomas-Fucking-Pynchon? Only his editor knows for sure.
And then there's the whole "Iceland spar" theme. It's obviously of some importance; there's a bunch of references to both it and "double refraction" throughout about the first half of the book. Hell, double refraction was important enough to be incorporated into the cover art on the dust jacket. But at some point he just drops the subject.
So, as I said earlier, I'm not sure what to make of it. Is it profound and subtle and just went over my head? Maybe, but I think I'm the audience he's aiming at. I got all the rambling about vectors and the Riemann zeta function, though I don't think I'd know a quaternion if it came up and bit me in the ass. Although I suspect that there's at least one more layer that requires more literary detective work than I'm interest in putting in. Many of the characters, especially the bit players, have names which are obviously intended to be read at multiple levels.
At any rate it kept me occupied for longer than the average tome. It's probably worth a read, if for no other reason than to provide something to talk about at your cocktail party.