Moon is a fine specimen of its kind, boasting virtually everything commercial J-rock has to offer: it's fast, it's emotive, it's heavy but not scary, and it's got more hooks than a fishing gear center.
Gackt can even do a somber track (in this case, "Fragrance"), which is a feat beyond the ability of many Japanese rockers who have trouble grasping the concept of "slow".
The problem is, this record is too fine and effective -- to the point where it becomes sterile.
The songs have the potential to cause a déjà vu on the first listen, and not because of plagiarism, but because they're that close to the archetype of pop music etched somewhere deep in the human brain, but this instant familiarity comes at the cost of identity -- Moon sounds too much like music in general; in other words, it's just too easy to get confused about whether you're listening to Gackt or to someone else.
It's even hard to pinpoint Gackt's style other than "modern J-rock," which is a vague description at best, despite the few musical connotations it actually possesses, although, as far as artificial (read: professional) Japanese music goes, Moon is definitely one monster of a record.