I have been reading some interesting material of late--that is, Luigi da Porto's original Novella about the Capellettis and Montecchis, as well as Bandello's re-write of the same--the bard's popular play follows it so closely, that it is impossible to think of him as "The Author" in the way that we understand that word--

Also read the Saxo Grammaticus History of the Danes, that is, the part that is the story of Hamlet, and found that the man, and his "madness" are there, as are most all of his adventures, including Mom and Ophelia--his curious character fully developed, hundreds of years before the Bard set quill to paper--

The true reason that Shakespearean authorship is so imprecisely credited may simply be that, in the time that the plays were current, the stories were so familar, and the sources of the works were so well known that "authorship" of the Shakespearean plays was not regarded as much of a literary achievement--being, perhaps, viewed much as we might view the "novelization" of a Star Trek episode--