As if a man fled from a lion, And a bear met him; Or he went into the house and leaned his hand on the wall, And a snake bit him.
Our own summary of these three verses is simply that the "day of the Lord" was to be bad news for Israel; and the great corollary of that is that it will be likewise "bad news" for the entire race of sinful and rebellious men.  The entire Book of Revelation might be interpreted as an extended commentary and revelation regarding this very passage in Amos. The theme of Revelation is "the judgment" of the great Day; and all of the figures that describe the onset of that occasion (of which there are seven) are those depicting unalloyed terror, slaughter, destruction, and sorrow for the near-total family of Adam who may live at the time it occurs.  Just one passage from Revelation is sufficient (of thirty that might be cited) to show how it will be for humanity at the judgment,  Amos 6:12-17.