Where can I get books for this exam?

I don't think your need any separate book for KCET , the question paper will comprise of questions in (Objective) Multiple Choice type format. The question paper (in each subject) will be in 16 different versions and each question asked will have four different answers from which you can select. The syllabus for PCM is as follows

PHYSICS

Unit I: Physical World and Measurement

Unit II: Kinematics
Unit III: Laws of Motion
Unit IV: Work, Energy and Power
Unit V: Motion of System of Particles and Rigid Body
Unit VI: Gravitation
Unit VII: Properties of Bulk Matter
Unit VIII: Thermodynamics
Unit IX: Behaviour of Perfect Gas and Kinetic Theory
Unit X: Oscillations and Waves

CHEMISTRY

Unit : Some Basic Concepts of Chemistry
Unit II : Structure of Atom
Unit III : Classification of Elements and Periodicity in Properties
Unit IV: Chemical Bonding and Molecular Structure
Unit V : States of Matter: Gases and Liquids
Unit VI : Chemical Thermodynamics
Unit VII : Equilibrium
Unit VII : Redox Reactions
Unit IX : Hydrogen
Unit X : S-Block Elements (Alkali and Alkaline earth metals )
Unit XI : Some p-Block Elements
Unit XII : Organic Chemistry – Some Basic Principles and Techniques
Unit XIII : Hydrocarbons
Unit XIV : Environmental Chemistry

MATHEMATICS

• Theory Of Indices And Logarithms
• Progressions
• Mathematical Induction
• Theory Of Equations
• Permutations And Combinations
• Binomial Theorem
• Partial Fractions
• Elements Of Number Theory And Congruences
• Analytical Geometry And Calculus
• Coordinate Geometry
• Calculus

• Measurement Of Angles And Trigonometric Functions
• Relations Between Sides And Angles Of A Triangle

You can cover these topics from anywhere beacuse I think it's not very different from the syllabus of MAINS .But according to me without practising some papers you can;t judge you level of practice so here is the link to last year question paper,

https://engineering.careers360.com/download/sample-papers/kcet-question-papers-2016

https://engineering.careers360.com/download/sample-papers/kcet-question-papers-answer-keys-2014-15