Hi
I dont think there is any eBOOKs specially for CAT preparations. There are few sites you can visit and get all the free notes , question papers and free mock tests with all the latest informations.
http://www.cat4mba.com i one of them & the best . All the coachin centers have thier ownsites, chk them u can get the url fro CAT4MBA.COM
Best of luck for CAT