Essential books for the UPSC preliminary exam usually include well-known publications such as the NCERT series for basic concepts, along with standard texts like "Indian Polity" by Subhash Kashyap, "History of Modern India" by Bipan Chandra, and "Economic Survey." For current affairs, reliable monthly magazines or compilations are advantageous. Such resources bolster aspirants' knowledge and provide a solid foundation to tackle the diverse syllabus effectively.