What are the reliable books and authors that help in going deep into the religion and striving in it, while avoiding the books of the Ash'aris, the Sufis, and those of deviant creeds?

Yes, that's what I wanted; for understanding in the religion is a sign of divine favor, and whoever Allah wishes good for, He grants him understanding in the religion. To achieve this, one must exert effort, organize time, and make a good choice of teacher and book, for knowledge is gained through learning. The only knowledge considered valid is that which is acquired from the Prophets and their inheritors, through the process of learning.