Interesting and multi-layered, but of uneven quality as there are multiple stories running at once, and sometimes more gimmicky than good. I recommend The Navidson Record, the film within the book, but not the surrounding stories.
Before the old, blind man died, he wrote (in many fragments) a critical analysis of a documentary that never existed. This is that analysis, decorated with the story of the broken fellow collecting it into a book. And a couple more levels.
The center-most level, The Navidson Record is a great haunted house story. I don't know to what extent that benefits from the pacing created by interspersing the other stories, but it works. It includes the most gimmicky formatting, including a labyrinth of footnotes and some other post-modern fun, but The Navidson Record is good.
I recommend reading it through the first ending or two. The story has several points where it could end, and it would have benefited from picking one of the earlier ones. If you get to the half-way point of the book, at least in my paperback "Remastered Full-Color Edition," you have extracted pretty much all the value from the book. Stop. After that point, there will be no fewer than three breather digressions before the final ending, and the last arc does not add much (except for the really fun post-modern moment of having a character in the movie in the book read and burn the book that contains him).
The manipulation of the page works nicely, as does the story it illustrates. Film it.
The Zampanò commentary level of the story is mixed and often tedious. Where it lays out character motivation and background in narrative form, it adds to the book. Other times it descends into academic nonsense, needless pretentiousness, or lengthy digressions that neither contribute to the story nor provide much interest on their own. To some extent, this is intentional and mocked within the book. That does not make it better or more interesting, although maybe you have read enough film school commentary to enjoy a send-up.
As pointed out in the book, a real commentary would not have this much detail about the film being critiqued. You get the entire Navidson Record, almost down to a shooting script. I expected to see more excised and left completely mysterious to the reader; it is to the story's benefit that it did not, but it makes the Zampanò level more irrelevant. Read the Zampanò parts that add background, skimm past the lengthy digressions (such as on echoes and labyrinths). Yes, that means skip anything
The Johnny Truant level is not good. At times it can be entertainingly salacious, but many of the early bits are annoying stream of consciousness rants. It picks up much later, but not enough to justify reading it all; just read Chapter 21, although that may not work as well without context. Your mileage may vary. If you have a horribly broken life and might sympathize with him, try a bit. He starts broken and gets far worse.
On the other hand, Johnny's story in the footnotes includes some great examples of going through panic attacks, told in the first person. If you loved Philip K. Dick's examples, you will enjoy Johnny's as well.
Courier is just not a fun font to read at length.
We have levels of unreliable narrators. Zampanò was blind, so he never saw The Navidson Record, and he might have been insane. The Navidson Record does not exist, even in the fictional setting; Johnny tells us it does not exist, the quoted books (mostly) do not exist, the quoted people never said that (when they exist). Johnny himself is variously a drunk, drug addict, habitual liar, and mental case, when noting having panic attacks and delusions. He also admits that he is not the most competent compiler of Zampanò's work and that he is not above changing it in a momentary fit of pique. Then there is a question of to what extent the documentary is a documentary, rather than in-world fiction, and how much manipulation the photojournalist might have done (either through framing or image manipulation).
And then, of course, the whole thing is a work of fiction that someone made up. At some point in the post-modern dance of many levels, one wonders whether it still matters. Does having that many levels make us stop caring, because it is a lie even within the fiction, or does it free us from caring about what is fiction or true and let us just enjoy it as a story? Fiction does not become less true for being meta-fiction. I wondered if Johnny was going to tell us at some point that he made the whole thing up, that there never was a Zampanò either; that might have been disappointing in a St. Elsewhere sense, but it's still a story either way. So don't worry about whether or not that happens.
The book elegantly finds another solution to Hofstadter's question of ending a book suddenly/surprisingly when the number of remaining pages is clearly visible. First, there are at least three levels of story going on throughout the book, so you can end two of those without warning. Second, the book also uses Hofstadter's idea of carrying on in the same vein after an ending. Post-modern books with odd formatting make that easy, and it gets easier when you start throwing in appendices and an overly long index.
There is another novella at the end. If an epistolary novel from a women in an asylum sounds good, feel free. By that point, I was not interested in another side tale that did not contribute to the core, so I skimmed in increasingly large jumps (except for the explicit puzzle letter; there are less explicit puzzles hidden). It is available separately.
The dedication page is great. Read at least that far. The index is notionally entertaining but not worth actually reading.
Haunted, the quasi-official soundtrack