God created language. God created emotions and feeling. These are, in and of themselves not sin. Arguably, the Psalms contain lyrical prose. Song of Solomon is without doubt lyrical prose. Job, Psalms, Proverbs, Ecclesiastes, and Song of Solomon are considered/ classified as books of poetry.
How much of Scripture is fiction? Remember the parable of the trees, Judges 9? This is not the recording of a true story. It is a fable. A story meant to teach a lesson.
Two works that are extremely good to read, and are both fiction, are Pilgrim's Progress and The Holy War. If you have not read them, I strongly recommend them. they are great examples of how fiction can be beneficial to a Christian.
Scripture is packed with non-fiction. not everything that is recorded is good (that it happened). It is not recorded in Scripture for us to repeat. It is there to learn from others mistakes and not repeat.
Principle 1
Ro 14:14 I know, and am persuaded by the Lord Jesus, that there is nothing unclean of itself: but to him that esteemeth any thing to be unclean, to him it is unclean.
While this talks about meat, if we think something is wrong to do and we decide to do it, we are deciding to do wrong. This is what makes the doing of doubtful things sin.
Principle 2
Ro 1:19 ¶ Because that which may be known of God is manifest in them; for God hath shewed it unto them.
Ro 1:20 For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:
Ro 1:21 Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened.
Ro 1:22 Professing themselves to be wise, they became fools,
Ro 1:23 And changed the glory of the uncorruptible God into an image made like to corruptible man, and to birds, and fourfooted beasts, and creeping things.
Ro 1:24 Wherefore God also gave them up to uncleanness through the lusts of their own hearts, to dishonour their own bodies between themselves:
Ro 1:25 Who changed the truth of God into a lie, and worshipped and served the creature more than the Creator, who is blessed for ever. Amen.
Ro 1:26 For this cause God gave them up unto vile affections: for even their women did change the natural use into that which is against nature:
Ro 1:27 And likewise also the men, leaving the natural use of the woman, burned in their lust one toward another; men with men working that which is unseemly, and receiving in themselves that recompence of their error which was meet.
Ro 1:28 And even as they did not like to retain God in their knowledge, God gave them over to a reprobate mind, to do those things which are not convenient;
Ro 1:29 Being filled with all unrighteousness, fornication, wickedness, covetousness, maliciousness; full of envy, murder, debate, deceit, malignity; whisperers,
Ro 1:30 Backbiters, haters of God, despiteful, proud, boasters, inventors of evil things, disobedient to parents,
Ro 1:31 Without understanding, covenantbreakers, without natural affection, implacable, unmerciful:
Ro 1:32 Who knowing the judgment of God, that they which commit such things are worthy of death, not only do the same, but have pleasure in them that do them.
If I were to undertake any writing, I would want to be sure that the things I were writing did not fall into the category of giving pleasure in reading the sins of others.(Romance novels are the major culprit in my opinion. the fact that some are called Christian doesn't sanitize them).
Edifying the hearers and helping people to understand attributes of God can be done without ever mentioning God. The book of Esther never mentions God. There is still a clear right and wrong. There is still the teaching of the providence of God in it and, while not crediting Him by name, it does not rob Him of credit either.