If married people do not view themselves as very best friends, then they are not loving like they ought to. We are one flesh, you can't get any better of a friend than that, you can't get any closer, any more meaningful or significant than marriage.
Beata: I love Kevin Leman's writing style! I believe not every Christian couple will agree with all of his views but I am sure that every couple will surely benefit from reading his books. He has wonderful books about parenting as well.