you should continue with old book but also study supplementary material which is available on icai site because all changes in company act 2013 available on supplementary material time to time. all minor changes can be covered by the latest RTP dont forget to study that. And wait for notification of all changes. https://www.icai.org/post.H T M L?post_id=10147
For Audit - Refer Sumit Aggarwal. New in market but wonderful book to secure maximum marks in minimum time. It also have short notes for quick revision & solved question for last 34 exams & PM. Presentation of SA, Co. Audit, & Professional ethics is excellent.
There are vast changes in Jan 15 Practice Manual of Audit in chapters of Audit report, Company audit, Liabilities of Auditors & Audit of Consolidated Financial Statements.
Moreover some more questions are added in every chapter.
I would suggest you to read from Jan 14 edition with Jan 15 edition so that you can see the changes while reading. Download pdf of Jan 15 Edition from ICAI's Website. I am also doing the same.
All the best!