There are lots of repeated questions asked in KEAM exam. I would suggest that you should buy a book of previous years question papers, so that you can see for yourself the repeated questions. I remember that there were lots of repeated questions, especially in Maths section. Here is a list of textbooks or reference materials you can buy:

Normal HSE/CBSE Textbooks

PREVIOUS YEAR SOLVED KEAM PAPERS by any local publishers

15 YEARS SOLVED PAPERS by Arihant Publishers