I will enlighten you a bit:
1 Nephi 13 (600 B.C.)
29 And after these plain and precious things were taken away [the Bible]it goeth forth unto all the nations of the Gentiles; and after it goeth forth unto all the nations of the Gentiles, yea, even across the many waters which thou hast seen with the Gentiles which have gone forth out of captivity, thou seest—because of the many plain and precious things which have been taken out of the book, which were plain unto the understanding of the children of men, according to the plainness which is in the Lamb of God—because of these things which are taken away out of the gospel of the Lamb, an exceedingly great many do stumble, yea, insomuch that Satan hath great power over them.
1 Nephi 14
10 And he said unto me: Behold there are save two churches only; the one is the church of the Lamb of God, and the other is the church of the devil; wherefore, whoso belongeth not to the church of the Lamb of God belongeth to that great church, which is the mother of abominations; and she is the harlot of all the earth.
Ether 3
14 Behold, I am he who was prepared from the foundation of the world to redeem my people. Behold, I am Jesus Christ. I am the Father and the Son. In me shall all mankind have life, and that eternally, even they who shall believe on my name; and they shall become my sons and my daughters.
Alma 7
10 And behold, he shall be born of Mary, at Jerusalem which is the land of our forefathers, she being a virgin, a precious and chosen vessel, who shall be overshadowed and conceive by the power of the Holy Ghost, and bring forth a son, yea, even the Son of God.
2 Nephi 2
22 And now, behold, if Adam had not transgressed he would not have fallen, but he would have remained in the garden of Eden. And all things which were created must have remained in the same state in which they were after they were created; and they must have remained forever, and had no end.
23 And they would have had no children; wherefore they would have remained in a state of innocence, having no joy, for they knew no misery; doing no good, for they knew no sin.
2 Nephi 5
21 And he had caused the cursing to come upon them, yea, even a sore cursing, because of their iniquity. For behold, they had hardened their hearts against him, that they had become like unto a flint; wherefore, as they were white, and exceedingly fair and delightsome, that they might not be enticing unto my people the Lord God did cause a skin of blackness to come upon them.
2 Nephi 25
21 Wherefore, for this cause hath the Lord God promised unto me that these things which I write shall be kept and preserved, and handed down unto my seed, from generation to generation, that the promise may be fulfilled unto Joseph, that his seed should never perish as long as the earth should stand.
You are right about one thing:
Joseph Smith added a whole slew of false teachings in two other books he called scripture!