Varience Analysis is beautiful topic. If one has some knowledge of Material , Labor and FOH, then it is easily understandable and marks giving topic.
Books for this topic
Cost Accounting by Matz Usry
Management and cost accounting by Collin drury

Almost all the topics of Cost Accounting can be covered from above mentioned books

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When you want something, all the universe conspires in helping you to achieve it. (Paulo Coehlo)