As a member of the LDS faith, I believe that the only way you can know if this religion is true is by direct revelation from God. The only things that have to be true for it to be true are 1) Jesus Christ is the Savior of the world and we must follow him, 2) The followers of the faith established by Jesus Christ fell into apostasy (that's easy enough to prove using history, the Bible and some of my personal experience on my mission) and 3) God called a prophet in Modern times and gave him the authority to lead His followers and perform ordinances required for salvation and the ability to give that authority through to others.
Well #'s 1 and 3 are not provable or disprovable through normal logical means. I think it's really cool that when some of the attacks against the Book of Mormon in the site I'm posting are disproven, they offer proof for its validity, but that still doesn't show the source of that miracle. That's something you have to find out for yourself by reading the Book of Mormon and praying about it and living the teachings that are in it.
you can request a copy at the bottom of this site