As per my opinion no special book is required to be referred for the preparation of case study. Focus on conceptual study and only refer scanner and case studies given in ICAI study material.
First prepare them and after that try other case studies.
SPECIAL ATTENTION TO SA AND AS Also give special attention to SA and AS. Only good knowledge of SA and AS is not enough but you must understand the technique to apply SA and AS in audit practical problems. For this purpose refer ICAI suggested answers and observe the application of SA and AS to the problem. Another benefit of this task isโit also helps you to understand SA and AS in a much better way.