Hello Devika,

Some of reference books links:

https://www.google.co.in/url?sa=t&source=web&rct=j&url=https://engineering.careers360.com/download/kcet-ebooks&ved=2ahUKEwi9o_LC47TaAhUKPI8KHTt2BCkQFjABegQICRAB&usg=AOvVaw02kYqyn-J1XqzXtG4WoH1A

Previous papers actually helps you to get moulded to the questions which they ask in examination.

Here are some previous papers:

https://www.google.co.in/amp/s/engineering.careers360.com/articles/kcet-sample-papers%3famp

Good Luck!