When to purchase book for Nov18 attempt ca final

In this regards, my recommendation would be to go to the market and see the content of the latest edition. Also, read ICAI notifications, whether any large ammendment is in the pipeline or not. If yes, then wait for the ammendment. Otherwise, it is not worth to wait for the small ammendments.

Thus I would recommend you to buy your books around April - May 2018.