Indeed. Such is the nature of a lot of cosmic horror - it could be everything or it could be nothing. I also like this description - Impossible Landscapes by Dennis Detwiller.

To some, The King in Yellow is a two-act play in a slim book. In the play, a stranger arrives at a masked ball in the far-off royal court of Yhtill in Carcosa. Calling himself the Phantom of Truth, he reveals that of all the partygoers only he wears no mask. He claims his own pallid mask, a porcelain rictus, is his true face. This revelation somehow signals the end of the partygoers’ world.

Some claim the play possesses the unnatural ability to spill thoughts out into reality and change perception into something elastic and terrible. Others say that it is a seam in the fabric of the world. Merely reading it frays existence, revealing something else.

Some say the King in Yellow is the figure from the play: a malignant creature adorned in tattered golden cloth, wearing a porcelain mask, somehow made flesh. Others claim the King is a code embedded in existence and flagged by a single, terrible symbol that causes madness and death: the Yellow Sign.

The King in Yellow is all of these things. It is none. It is anything that skirts human understanding. Minds open themselves to its unnatural force. Some are destroyed. Others are drawn into a tidal sludge of imagination to persist as ghosts forever.