Isaiah 9:3
The Book of Mormon really helps to clarify certain things. Look at Isaiah 9:3 in the Old Testament and that same verse in the Book of Mormon. Notice it does not have the word 'not' in the Book of Mormon. Now the scripture makes sense, otherwise one would wonder why the Lord would multiply the nation but not give them joy.
What other scriptures or doctrines do the Book of Mormon help to clarify for you?
For me, it has always been interesting to note that the word 'atonement' is mentioned only once in the new testament (in Romans). I believe one of the main purposes of the BOM is to clarify and teach more about the the most important act in all human history- that is the 'atonement' of Jesus, The Christ.
The BOM does not disappoint in this regard. It's full of explanation and description (2Nephi, Alma, Mosiah etc etc.).
This is something not found in the Holy Bible as it has been translated and handed down to us over the years. For me, it's the most attractive element of the BOM.
The Book of Mormon really clarifies in my mind that the people spoken of and the contributors to the Book of Mormon records are the 'other sheep not of this fold." Heavenly Father has always known who His people are and where they have been scattered, whether or not we do. Without the Book of Mormon to help me to understand the following scripture, it would probably be confusing and more difficult to understand.
John 10: 16 "And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd."
Clarifying scriptures in the Book of Mormon:
3 Nephi 15:21 "And verily I say unto you, that ye are they of whom I said: Other sheep I have which are not of this fold; them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd.
3 Nephi 16:1 "And verily, verily, I say unto you that I have other sheep, which are not of this land, neither of the land of Jerusalem, neither in any parts of that land round about whither I have been to minister."
For me the Beatitudes in 3 Nephi clarify them better then what they say in Matthew.
Matthew 5:3-11
Blessed are the poor in spirit: for theirs is the kingdom of heaven.
Blessed are they that mourn: for they shall be comforted.
Blessed are the meek: for they shall inherit the earth.
Blessed are they which do hunger and thirst after righteousness: for they shall be filled.
Blessed are the merciful: for they shall obtain mercy.
Blessed are the pure in heart: for they shall see God.
Blessed are the peacemakers: for they shall be called the children of god.
Blessed are they which are persecuted for righteousness' sake: for theirs is the kingdom of heaven.
Blessed are ye, when men shall revile you, and persecute you, and shall say all manner of evil against you falsely, for my sake.
Here's how it's layed out in 3 Nephi 12:3-11
Yea, blessed are the poor in spirit who come unto me, for theirs is the kingdom of heaven.
And again, blessed are all they that mourn, for they shall be comforted.
And blessed are the meek, for they shall inherit the earth.
And blessed are all they who do hunger and thirst after righteousness, for they shall be filled with the Holy Ghost.
And blessed are the merciful, for they shall obtain mercy.
And blessed are all the pure in heart, for they shall see God.
And blessed are all the peacemakers, for they shall be called the children of God.
And blessed are all they who are persecuted for my name's sake, for theirs is the kingdom of heaven.
And blessed are ye when men shall revile you and persecute, and shall say all manner of evil against you falsely, for my sake:
While some of them are as obviose as the nose on our face others are over looked because it is simply one word.