I find the practice of reviewing a book before you're done with it rather silly, but the book in question is massive and I'd like to get this down to see if my opinion changes by the end (which might be a long time.)
Infinite Jest: so far, a bit all over the place. Too much detail, too many characters, and too much covered. I suspect that's the point--but as the reader, being bludgeoned into submission isn't so far too enjoyable. By page 300 (and the pages are large with small print), there are still new characters, new styles, and new themes being introduced. I find the possibility of a satisfactory ending--in which all the threads are tied off in some sense--remote.
With that said, the writing is excellent, the characters are interesting, if slightly too fucked up and intelligent. It's fun to read, which is a major plus for "literary" fiction. (I find Pynchon like reading a mashed potatoes/cement mixture.) It's also very funny.
Stay tuned for the wrap-up.