I'm a big PKD fan, having read pretty much every one of his scifi book (of which there are many), but even I wouldn't recommend The Exegesis to any but the most die-hard fan.. and even then I doubt most of them could make it through much of that book before shelving it and reading something else.

It's basically a really, really, reaaaaaaly looong, barely coherent book of random ramblings. It's fine to dip in to now and then to see what PKD was thinking about on any random day, but really hard to stomach reading very much of, as unlike a fiction work it has no structure, no characters, no plot, and was not intended for anything but a private sounding-ground for the author to spitball ideas, many of them having to do with one event that PKD probably dearly wanted to be a mystical experience and that he just couldn't seem to drop and move past.

To truly die-hard PKD fans this might be endlessly fascinating, but to me it's only worth peeking in for maybe a few pages every few years or so. I can't imagine reading the whole thing, even if it was the only book I had on a desert island.