How do Mormons interpret the warning in Revelation about adding to the book? How do Mormons interpret the following passage and justify the addition of the Book of Mormon to the canon of scripture?


  Revelation 22:18-19 (NIV)
   18 I warn everyone who hears the words of the prophecy of this
  scroll: If anyone adds anything to them, God will add to that person
  the plagues described in this scroll. 19 And if anyone takes words
  away from this scroll of prophecy, God will take away from that person
  any share in the tree of life and in the Holy City, which are
  described in this scroll.


In my experience, this is interpreted as referring to the entire Bible and how we should not add to or remove from it. How is the LDS view on this different?
Your premise is invalid, as the warning in Revelation cannot be honestly interpreted as referring to anything beyond Revelation itself.  "The Bible" did not exist back then.  The very concept of "the Bible" did not even exist back then.  Each sacred writing was its own book; they weren't compiled into a collection until centuries later.  In addition, John wrote the Gospel of John after he wrote Revelation.  An overly-broad interpretation of the warning at the end of Revelation would invalidate the most beautiful and profoundly spiritual of the four Gospels!