Haven't seen it lately but I used to see ads frequently, on TV, stating just exactly that,"The Book of Mormon, another gospel of Jesus Christ".
Correction to my earlier reply:
Upon reflection, I believe those ads I spoke of did not say, “B.O.M, another Gospel of Jesus Christ” but instead said, “Another testament of Jesus Christ”.
An error of memory on my part and not intentional. Big difference in the words, “Gospel” and “Testament” and I apologize for the mistake.
I still believe the B.O.M. to be one huge false testament.
Not a replacement Gospel.