I thought "The Throat" was one of the best-written novels ever published, lots of complexity, mysteries within mysteries, satisfying ending, finely drawn characters, all over a fun experience. My impression of "The Talisman" and "Black House," collaborations with Stephen King, was that they were superb. "Shadowlands" was a confusing miasma but had an interesting premise.
(update several days later) To tell you the truth, I went online to see if I could make sense of my confusion regarding "Mr. X." . Turns out, after all, I wasn't too far off the mark regarding the major characters and events and underpinnings. OK, more stuff:
"Mr. X" was along the same lines as "Shadowlands," confusing and difficult to read in many spots. However, that said, I must state that this work is peopled with some of the quirkiest characters I've seen in a novel. This is true mostly of the protagonist, Ned Dunstan's, extended family, one wackier than the rest, and some with some parapsychological....well, I'll let you discover that for yourselves. A major minor character who comes along in the second half of the book is a crusty old attorney with great senses and an extremely unflappable nature, who seems to know all about the families and their strange, complex natures, as well as the small town they inhabit. One of my favorites! We all could use someone like that in our corner.
(further update, which I forgot to add earlier. This getting older is REALLY inocnvenient!) Much of the book's basis relates to "The Dunwich Horror," which was written by H. P. Lovecraft in the 20's and relates to a theory that there are "the Old Ones" who are aliens from another planet who influence and are personified in some contemporary people. I saw the movie when it came out in the 70's and enjoyed it, and I have also read some other Lovecraft. It's neat to see Straub have some fun iwth Lovecraft, but unfortunately it doesn't save the work.
Sooooo, even with my misgivings, this one doesn't turn me away from Mr. Straub (after all, I've also read some clunkers by Messrs. Koontz and King and I still come back for more). I believe "Julia" and "The Hellfire Club" have gotten good reviews, so I'll get to them in due time.