Took me a lot longer to do the puzzles than I would have liked. It seemed to me like the game went on for longer than it needed. I also didn't really bother to read most of the books after a while since it seemed like most of the info was pointless.
I managed to finish the game but it must have taken me at least an hour and a half if not longer.
By the time I got about half-way through nothing really scared me anymore. The environments were interesting but nothing was really terrifying, it just looked cool.
Most of the reason I took so long was because a few of the puzzles are barely explained. One where you need to look at typos in the text, another where you need to look into some rooms and randomly count the number of objects in them.
None of this is to say I don't think its a good game, I did enjoy it. The style is well executed, the voice acting is great, and the environments are awesome. But for a horror game, this didn't really scare me at all.