  In this article we study pluriregular varieties X of general type with
base-point-free canonical bundle whose canonical morphism has degree 3 and maps
X onto a variety of minimal degree Y. We carry out our study from two different
perspectives.
  First we study in Section 2 the canonical ring of X describing completely the
degrees of its minimal generators. We apply this to the study of the projective
normality of the images of the pluricanonical morphisms of X. Our study of the
canonical ring of $X$ also shows that, if the dimension of X is greater than or
equal to 3, there does not exist a converse to a theorem of M. Green that
bounds the degree of the generators of the canonical ring of X. This is in
sharp contrast with the situation in dimension 2 where such converse exists, as
proved by the authors in a previous work.
  Second, we study in Section 3, the structure of the canonical morphism of X.
We use this to show among other things the non-existence of some a priori
plausible examples of triple canonical covers of varieties of minimal degree.
We also characterize the targets of flat canonical covers of varieties of
minimal degree. Some of the results of Section 3 are more general and apply to
varieties X which are not necessarily regular, and to targets Y that are
scrolls which are not of minimal degree.
