I believe the tag line for this book “Are you brave enough to enter?” is pretty appropriate. This is a question you should ask yourself as well as a warning that you might not find it as easy to sleep at night as you did before.
That you might enter a nightmare.
That you might be afraid.

All these are true.
None of the Dean Koontz books I have read have stuck with me the same way this one has. Similar to Stephen King and Peter Straub’s The Dark House, Stephen King’s Overlook Hotel (the Shining) and also very similar to another of Dean Koontz’s Odd Thomas novels (the Apocalypse one) and strangely, I can also see some of the things in common with the loops of Miss Peregrine’s Peculiar Children, this book will chill you.

Enter the world of the Pendleton, a beautiful limestone Gilded Age
palace that’s been converted into a set of highly desirable
condominiums. Its tenants feel lucky to live there. Yet luck and the
Pendleton have little in common–its years have been colored by madness,
kidnappings, murder, and strange, inexplicable accidents. But all of
that is in a past mostly unfamiliar to the people of the Pendelton. To
them, their building is a sanctuary…. That is, until it turns on them.
Shadows with no source begin to skitter across the walls, voices whisper
in unknown languages, security cameras show impossible feeds, and a
little boy starts talking to an imaginary playmate, who turns out to be
all too real. These are only prelude to a terror that will soon fully
engulf the tenants of Pendleton, in an unimaginable world from which
there may be no escape.

But now inexplicable shadows caper across walls, security cameras relay impossible images, phantom voices mutter in strange tongues, not-quite-human figures lurk in the basement, elevators plunge into unknown depths. With each passing hour, a terrifying certainty grows: Whatever drove the Pendleton’s past occupants to their unspeakable fates is at work again. And as nightmare visions become real, as a deadly tide begins to engulf them, the people at 77 Shadow Street will find the key to humanity’s future . . . if they can survive to use it.

“Fear is the engine that drives the human animal. Humanity sees the world as a place of uncountable threats, and so the world becomes what humanity imagines it to be. They not only live in fear but use fear to control one another. Fearmongering is their true religion.”

Not sure if this would have been a more appropriate post during Halloween, to scare the people off, but now that Valentine’s day is done and over, people who felt like there was too much love in the air and they need a refreshing break, can check in into this hotel that features inter-dimensional travel, a set of fast-moving monsters, a slip in time (both backwards and forwards) and a cast of characters so diverse, you will feel connected to at least one of them.

“Death was everywhere, he was legion, and you couldn’t escape his attention, but in some places he manifested in greater numbers than in others.”

While many people have complained about the length of the book and the padding out, I would say it wasn’t as dragged out as Under the dome and there was always something happening. The characters all have back-stories and even if they disappear through the plot, they always emerge up to help and be reunited with the others. The hotel is truly haunted and the beasts that kill the inhabitants one by one are appearing with a greater frequency, signalling that the house is about to either collapse on itself or be propelled into a world with no sun.

“Either the gates of hell had opened, or Tom had lost his mind; for there could be nothing like this entity outside the precincts of the damned, except in the fevered fantasies of a raving paranoid psychopath”

This is not an anti-science story, it’s a cautionary tale, to me more about dangers of science disconnected from morality than the Crichton-esque “man creates something he can’t control” tale, although there’s obviously some of that as well.

Ignis and Norquist are both guilty in different ways, which is why both had to die. Norquist’s goal was to reduce the size of humanity which he viewed as a plague on nature. So he came up with a way to have fewer people by making them immortal.

When he finds out of the future, he’s satisfied instead of horrified. Ignis is the lesser of two evils as he doesn’t hate humanity. He want to use science for good, but he’s arrogant enough to think he can unleash this technology on the world and risk this future after having seen it. This still makes him dangerous. Not because he invented something, but because he refuses to see the danger when it’s right before his eyes.