And it's not looking too pretty. The New York Times review begins:
Thomas Pynchon’s new novel, “Against the Day,” reads like the sort of imitation of a Thomas Pynchon novel that a dogged but ungainly fan of this author’s might have written on quaaludes. It is a humongous, bloated jigsaw puzzle of a story, pretentious without being provocative, elliptical without being illuminating, complicated without being rewardingly complex.
You can read the rest here.
Also see the New Yorker review.