Hi Jen:
If you have 2017 book, I don't think you need to buy new book. Just take note what is changing between 2017 and 2018. Here's what I found from RogerCPA website:
Auditing and Attestation (AUD)
Blueprint: There were no new content areas added or removed from the AUD Blueprint for 2018. However, one content group and 12 representative tasks have been revised to reflect the terminology changes in SAS 130, An Audit of Internal Control Over Financial Reporting that is Integrated with an Audit of Financial Statements. For example, under Area IV, A, 3, the task has been changed as follows: “Prepare a draft report for an examination of internal control engagement or for an audit of internal control integrated with the audit of an entity’s financial statements, starting with a report example (e.g., an illustrative report from professional standards).”
Content: The AUD section of the Exam will see some notable changes for 2018. Our team has been hard at work overhauling relevant course materials to ensure candidate success:
SAS 132, The Auditor’s Consideration of an Entity’s Ability to Continue as a Going Concern (AU-C 570)—Eligible for testing Q1
SAS 133, Auditor Involvement With Exempt Offering Documents (Amends AU-C 560 and 925) —Eligible for testing Q3
Good luck,
Maria