As a member of the Church of Jesus Christ of Latter-day Saints (Mormon) , can I just clarify our position regarding the Bible.
We believe the Bible to be the word of God. We use it as a primary source of scripture and follow it's teachings. We generally use the King James Version of the Bible. We believe, however, in the translation process, certain truths have been lost etc from the original texts as they have been translated from one language to another to another.
Joseph Smith, did give his personal interpretations on some elements of the Bible, particularly the Gospel of Matthew - this was simply clarification - we still use the King James Version as our primary Biblical text. Many may dismiss Joseph Smith's clarification, but isn't it similar to many modern day versions of the Bible which have someone's opinions of the original meaning as they have prepared it for a more modern audience?
We also believe in the Book of Mormon (hence the nick name of he Church), the history of a small group of Jews who left Jerusalem at the time of Jeremiah, approx 600BC, which, like the Bible recounts the account of God's dealings with them. Central to the Book of Mormon is the account of the Saviors appearance to them after His resurrection.
We believe the Book of Mormon goes hand in hand with the Bible as a second witness that Jesus Christ is the Savior of Mankind. We use it to more fully understand the doctrines of the Bible.
It in no way replaces the Bible.
I hope this clarifies your question as far as the use of the Bible by members of the Church of Jesus Christ of Latter-day Saints (Mormon)