This Book of Aptitude & Reasoning has been designed to meet the growing requirements of candidates appearing for GATE & ESE (Prelims) 2023. The book also satisfies the need for candidates appearing in UPSC (Prelims), Bank (PO), SSC, MBA entrance exams, and various software companies' campus placements. This comprehensive volume covers Topic-wise Theory with Solved Examples, Practice Questions, and Previous Years' GATE & ESE (Prelims) questions of various engineering streams, such as CE, CH, CS, EC, EE, IN, IT, PI and ME. The book consists of seventeen chapters with a significant focus on questions from Arithmetic, Ratios, Progression, Polynomials, Permutation & Combination, Clocks & Calendars, Dice & Cubes, Basics of Geometry, Blood Relations, Puzzles, Data Interpretation, Venn Diagram & Syllogism, and Critical Reasoning.