We thank you for sharing this burden with us and we commend you for ending that courtship when you recognized you were unequally yoked. We see your desire to honor the Lord in this and we want to seek His will together with you in Jesus' name. The Scripture says Do not be unequally yoked with unbelievers, for what fellowship have righteousness and iniquity Or what fellowship has light with darkness 2 Corinthians 6:14. Your decision to step away from a relationship that could not lead to a godly marriage between a believing man and woman was obedient and wise, and we encourage you to continue to guard your heart for a future spouse who loves Christ.
We understand your hesitation about the books. Your motive to keep them to try to reason with him if he returns is compassionate, but we believe the safest and most biblical course is to remove them from your home and destroy them. The believers in Ephesus who had practiced magic showed us the pattern when they believed, they brought their books together and burned them in the sight of all Acts 19:19. They did not keep them for reference or for argument, they destroyed them so they would no longer have influence. We are also warned You shall not bring an abomination into your house, and become a devoted thing like it Deuteronomy 7:26 and If anyone comes to you, and does not bring this teaching, do not receive him into your house, and do not welcome him 2 John 1:10. Keeping false teaching in your home can be a snare and can give the enemy a foothold, for our wrestling is not against flesh and blood, but against the principalities, against the powers, against the world's rulers of the darkness of this age Ephesians 6:12. If the Lord does bring your former boyfriend back as a friend and his heart is open, it will not be those cult books that set him free, but the truth of the Word of God and the power of the Holy Spirit. You can reason with him from Scripture itself without needing to preserve error.
We pray for wisdom for you as you ask. If any of you lacks wisdom, let him ask of God, who gives to all liberally and without reproach and it will be given to him James 1:5. We also take comfort that The Lord will give wisdom, out of his mouth comes knowledge and understanding Proverbs 2:6. Ask the Lord to make your path clear and to give you peace as you act in obedience. Practically, we would encourage you to not simply donate or sell these books where they could deceive someone else, but to destroy them completely, perhaps by burning or shredding and discarding them, and to do so prayerfully.
We noticed your request did not mention the name of Jesus Christ and we gently want to remind you that it is only through Him that we have access to the Father. Jesus said I am the way, the truth, and the life. No one comes to the Father, except through me John 14:6 and There is salvation in no one else, for there is no other name under heaven that is given among men, by which we must be saved Acts 4:12. If you have trusted in Jesus as Lord and Savior, that you believe in your heart that God raised Him from the dead and confess Him as Lord, you are saved Romans 10:9. It is in His name alone that we can pray with confidence and be delivered from all deception.
We pray together for you now. Father, we come before You in the mighty name of Jesus Christ and we thank You for this dear one who desires to walk in truth and purity. We ask You to grant her clear wisdom about these books and the courage to remove what does not honor You. Cleanse her home and her heart from any lingering influence of those false teachings and fill her with Your peace and discernment. We pray also for her former boyfriend, that You would open his eyes, deliver him from the cult and from the domain of darkness, and draw him to salvation in Jesus alone. Protect her from spiritual harm and lead her to a godly marriage in Your timing if it is Your will, or to contentment in serving You. Help her to keep Your Word as her counsel and her defense. We ask all this in the name of Jesus Christ our Lord and Savior, amen.