In the novel, the picture window never breaks.The window that has all the Faux Shadowing towards being broken survives the boiler explosion. It is shielded from shattering by a miraculous confluence of events and a heavily faulty frame, and the pane itself ends up slicing into a dense snow drift some ways away completely undamaged.
The Overlook Hotel is an entity like 1408...... only all grown up.
Ulman and Watson knew the Overlook was haunted.The way they talked to Jack about it was like they were hiding something. Scandals are one thing, but they seemed frightened by what they are hiding.
Ulman not only knows about the hauntings, he has made a deal with the entity and all it's ghostly representations.He feeds it souls and psychic energy and they don't bother his guests for the summer season, save fore a few glimpses. Why else would the hotel be somewhat normal in the summer, but piss your pants scary in the winter?
The Overlook is the nesting site of a powerful Bane spirit.The "burial ground" explanation was a mistranslation by the white settlers. Unfortunately when the hotel was built, the native protesters who were killed included the Uktena Bane Tender who was keeping the... thing sleeping under the earth.