You can use the 9th edition to study for the exam. Make sure that you review the errata list, which can be found at www.studymanuals.com.
Some improvements were made in the 10th and 11th editions, as follows:
10th Edition
- Section 16b (Put-Call Parity) was revised and expanded to make the concepts easier to understand.
- Section 16c (Combining Options) was completely re-written and greatly expanded to make it easier to remember how to construct the various strategies (straddles, strangles, spreads, collars, etc.).
- The solutions to about 70 problems in Section 1 to 4 were revised for greater clarity.
11th Edition
- About 50 ADAPT questions were added as in-section examples.
- Additional questions on duration, convexity and immunization were added to the original practice exams because of student feedback that there have been a surprising number of questions on these topics in recent exams.
- A 6th original practice exam was added.
- A new set of Calculator Notes on the Cash Flow worksheet (NPV and IRR) was added.