Readers agree about this card more than about almost any other, which is itself notable in a system where agreement is rare.
The core reading is a sudden collapse of a structure that could not have survived anyway, arriving from outside and without warning. The emphasis is on both halves: it is sudden, and it is not arbitrary. What the lightning takes down was already unsound, and the shock is the discovery rather than the cause.
The disagreement is about consolation. One school reads the card as ultimately liberating: what falls was a prison, the fall is the release, and the querent will be better off once the dust settles. The other school declines to offer that, on the grounds that a person who has just lost something does not need to be told it was good for them, and that the card is describing a loss whether or not it is survivable. The second position is harder and is more common among readers with long practice.
A narrower and often overlooked reading is revelation: something said, or found out, that cannot be unsaid, after which the previous arrangement is not available. This fits the letter Peh, the mouth, and it fits a great many actual spreads.
Waite's reversed meanings soften the card towards oppression, imprisonment and a disaster in lesser degree, rather than cancelling it. Readers who do not use reversals generally take the position that a card about the uninvited does not become optional by being turned around, and read it upright regardless.
The one thing worth resisting is the modern habit of treating the Tower as exciting. It is a card people are frightened to draw, and they are not being superstitious when they are.