Mormonism as the 4th Abrahamic world religion?

Alongside Judaism, Christianity, and Islam...

That's Richard Land's assessment anyway-- as recorded at Time.com (hat tip: Touchstone)...

In a sense, this works quite nicely. As Land notes, he sees Mormonism...

as another faith in the same sense that I would look upon Islam as another faith. I think the fairest and most charitable way to define Mormonism would be to call it the fourth Abrahamic religion — Judaism being the first, Christianity being the second, Islam being the third, and Mormonism being the fourth. And Joseph Smith would play the same character in Mormonism that Muhammad plays in Islam.

Land doesn't see Mormonism as a cult, defining that category as...

a form of faith which does not comply with the essential teachings of the Christian faith but claims to be within the Christian faith or to be the true expression of the Christian faith, as opposed to being another religion like Judaism.

By that definition, Mormonism self-qualifies (as perhaps does Catholicism, some within Church of Christ, and other smaller groups). One difficulty here is defining "essential teachings". Another is the distinction between official doctrine, how that doctrine is disparately communicated, and how that doctrine is understood by its professing members.

For example, one can go to a variety of churches within, say, Catholicism-- and ironically, here quite different ideas on the role of faith and works in salvation.

Among professing members, Barna's research is interesting. In particular, he found that among self-identifying members, Mormons are equally likely to believe what he determines are the essentials of the Christian faith as Catholics-- and more likely than Episcopalians. If that's the case-- and one considers Mormonism a cult (or another religion, to accept Land's distinction), what does that make Episcopalians?