Actually, if you derive a moral lesson from reading or watching a production of Macbeth, you do "believe" it. The literalistic adulation most Xians have been taught to give the bible misses its true value.
If you read the law, deuteronomic history, prophets, later writings and wisdom literature from the Hebrew bible and Septuagint (Greek translation use in the Roman era), you can trace the evolution of Judaism from a tribal cult religion to a system of universal ethical principles that does not even require belief in the supernatural. Unfortunately, Christianity was hijacked by an authoritarian sect that thrives on fear and superstition.
I take it you mean to imply the bible is not well written. By the standards we apply to Shakespeare, it can't be: it is the work of more than fifty authors over a period of more than 1,000 years.
Genesis alone had at least four "original" authors (groups of authors is probably more accurate). Then the redactors took these variant traditions and put them together in a way that preserves their individual perspectives yet reveals a common theme. Not bad, when you think about it.
Each of those consists of a single literary genre: Homer is epic poetry; Herodotus is historical chronicle; Plato is philosophical dialogue. Comparing the bible to one of those is like comparing hummus to a salmon steak. Each is what it is.
Most outspoken atheists I encounter seem to wear their ignorance of the bible and other religious scriptures like a badge of honor. In fact it makes them come across as ill informed and narrow minded when they argue against religion. But for poetry & sublime prose, I would suggest Psalm 137 & 1 Corinthians 13. Genesis 37.1 - 46.27 is a story line with interesting plot twists and good character development.
There is more porn in the bible than in Macbeth.
Given the choice, I think I would prefer my kids to learn lines like "out damned spot" than "There she lusted after her lovers, whose genitals were like those of donkeys and whose emission was like that of horses" which appears in both Ezekiel 23:20 and, coincidentally, Penthouse Letters, Volume 7 at page 14.
Religionists don't believe because of the content of their book. For most of history they could not even read their book. Most of them believe in spite of it. The contents of the book are largely irrelevant.
In the case of MacBeth, we know who the author is and we know it was intended as a work of fiction. I think a better analogy would be the tales of King Arthur and the Knights of the Round Table. The origin of the King Arthur story is unknown and there is insufficient evidence that an actual British king named Arthur existed.