Carefully compare your book's content to the exam topic list CCNA Exam Topics and then figure out your gaps. Ultimately you want to cover as much of that list as possible. If you do not have the resources to purchase the new book either fill the gaps with content from cisco.com and the Internet or sign up for a 1 month trial of Safari and look for 200-125 material there.
I would also highly recommend reviewing the following document: CCNA Routing and Switching Refresh
It provides comparison between the CCNA R&S v2.0 and v3.0 exams with information on which topics were removed/added.
Good luck on your exam preparation!
Cisco Learning Network Moderator