I have many books I read but of course the #1 is the bible. I have and am reading several versions of the bible and one knows they are serious when I started TWO bible reading plans simultaneously. I mean, some people have trouble reading thru the bible in a year. Now, I've read it so many times it's more like 8-9 months per reading and even down to 6 months on occasion.
That said, I like to read religious esoterica for want of a better term. I had 26 books I considered special, but could be streamlined to 5 major books:
One book (I reread on occasion) is Judah's Sceptre/Joseph's Birthright by J.H. Allen. In this politically correct climate it's a book best kept to private reading-- I don't talk much about it any longer. I laugh when Amazon proudly sells it without knowing what's in it. But the book was written over 100 years ago in the height of the American and British Empire, and more people were Christians and not afraid to say so. It was the start of our mission work, bible societies and world colonization and power.
The second is a book by H. W Armstrong about the end times and why we are waning and the warnings it gives along with the glorious future of the coming Kingdom of God.
I like some of the 19th century theologians one being E. W Bullinger. His book is "Witness of the Stars" or God's Word told in the stars by virtue of stellar and constellation names. It depicts the bible story from ancient times.
Lastly, I have a pyramid book where some theologians believe the Great Pyramid is not really a product of Egypt, but rather God's message in stone (c.f. Isaiah 19:19-20). There are no shortages of books about the pyramid so one has to take it with great caution because it can be misrepresented. It's the math in me that takes a liking to this. Sir Isaac Newton had a similar interest in the pyramid in the context to find a measurement (cubit) related to the dimensions of the earth for his work in physics. But Newton also had interests in these same subjects and applied that to the Temple in Jerusalem and the like.
Of course, the last book is really the first, the bible as I already mentioned. These types of books give one a glimpse of the subject matter I like to read and the "Sir Isaac Newton" interests in me.