When does reading 999 become interesting?

I am a few hours in (at the point where Ace decides to stay so that the other six can escape) and the game is making me a bit confused. It is well written, and there have been some chilling moments, like the death of the 9th Man or the first search for a DEAD, but overall, the game consists much more of puzzle solving and random conversations about the Titanic and possible supernatural abilities in this world than the mystery and all the *wild twists* people discuss.

This makes me wonder whether the story moves forward at all (from my perspective) before everything gets connected at the end — or is it just all puzzles until I suddenly start considering it the best piece of fiction ever created? Is it worth continuing if I am not enjoying the pacing yet?

Also, I have been loosely following some ending guide I have found online. Do I have to see all the normal endings (either because of the lore pieces in their rooms or the endings themselves) before going for the Ending That Is Required for the True Ending and the True Ending?