If the book portrays God in the feminine and the Bible says God is masculine then the very basis of the book is blasphemous. Even if the book has a good message, does the end justify the means? The Apostle Paul addressed this in Romans 3:8 "And not rather, (as we be slanderously reported, and as some affirm that we say,) Let us do evil, that good may come? whose ****ation is just." God's inspired word calls it a slanderous report for someone to even accuse a Christian of doing something wrong to bring about something good. I believe this verse also makes it clear that to do such a thing is worthy of being sent to hell.
As for saying this that it's ok for a mature christian or avid reader but not someone new to the faith, I believe scripture addresses that as well:
(For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds
Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ; And having in a readiness to revenge all disobedience, when your obedience is fulfilled.
2 Corinthians 10:4-6
The knowledge of God, gained from his personal revelation in his Word, clearly states that God is masculine. Therefore this book exalts itself against the knowledge of God. The cry of it being ok because it's fiction does not fly because this passage clearly includes imaginations. No thought that is in obedience to Christ would blaspheme God or make any change to how he is revealed in Scripture. The God revealed in scripture is the unchanging God(Mal 3:6), the same yesterday today and forever(Heb 13:8), with no variableness or even shadow of turning(James 1:17). Therefore, no mature Christian or avid reader should read this book because to do so would be entertaining thoughts that are in disobedience to Christ and exalted against the true knowledge of God.
My people are destroyed for lack of knowledge: because thou hast rejected knowledge, I will also reject thee, that thou shalt be no priest to me: seeing thou hast forgotten the law of thy God, I will also forget thy children.
Hosea 4:6
And Samuel said, Hath the LORD as great delight in burnt offerings and sacrifices, as in obeying the voice of the LORD? Behold, to obey is better than sacrifice, and to hearken than the fat of rams. For rebellion is as the sin of witchcraft, and stubbornness is as iniquity and idolatry. Because thou hast rejected the word of the LORD, he hath also rejected thee from being king.
1 Samuel 15:22-23
May none of us ever feel so mature in Christ that we feel we can set aside such clear commandments in scripture. We are kings and priests unto our God. May we not think that are mature enough to set aside the knowledge of God and be entertained by knowledge contrary, lest God reject us for our rejection of true knowledge and forget our children. May we not make ourselves just as bad as, or participate in, witchcraft by our disobedience to God's clear instructions which are for our own good.
My prayer is:
That the God of our Lord Jesus Christ, the Father of glory, may give unto you the spirit of wisdom and revelation in the knowledge of him: The eyes of your understanding being enlightened; that ye may know what is the hope of his calling, and what the riches of the glory of his inheritance in the saints, And what is the exceeding greatness of his power to us-ward who believe, according to the working of his mighty power,
Ephesians 1:17-19