Gospodar svetlosti (Lord of Light), written by Roger Zelazny in 1967, is widely considered one of the greatest science fiction and fantasy novels ever written. It won the prestigious Hugo Award for Best Novel
The Master of Light: A Review of Roger Zelazny's "Gospodar Svetlosti"
Internet Archive: You may be able to "borrow" a digital copy for free through the Internet Archive's Open Library.
Classic Sci-Fi Book Cover: “Lord of Light” - Ash Clifton, Writer