I cleared my CC exam yesterday, took 3 months of preparation (1hr a day). I found exam was not hard not easy but the main catch was english words. need to give extra efforts to understand the questions.
I feel that official ISC study material is not enough to understand the concept, i took thor's CC course and it gives me a better understanding.
Special note: keep your stress and worries at home when you go for exam. if you understand questions well then you will pass.