How does one deal with those who are nearly innovators, especially the innovation of saying the Qur'an is created? And what are the reliable books by trustworthy scholars that have extensively refuted the people of innovation on this issue?

It is not possible to fully discuss the issue of the creation of the Quran within the scope of a fatwa. One can refer to previous fatwas on this matter. It is better to consult a specialized research paper or book. Among the most prominent scholars who addressed it is Ibn Taymiyyah in the twelfth volume of his collection of fatwas, and his discourse was summarized by Abdul Rahman Al-Mahmoud in his treatise (Ibn Taymiyyah's Stance on the Ash'aris). Other books include: the treatise (Al-Haydah wal-I'tidhar) by Abdul Aziz Al-Kinani, and the book (Al-Aqeedah As-Salafiyyah fi Kalam Rabb Al-Bariyyah) by Abdullah bin Yusuf Al-Judaie. These books are available on Al-Maktaba Al-Shamilah.