Significant changes were made in the past several years to both the SSAT and the ISEE. Only three SSAT/ISEE prep books on the market have printed new editions that addressed these changes: this book (Kaplan), the Princeton Review book, and the SSAT/ISEE for Dummies. This is definitely NOT the best of the three.
The practice tests in this book do reflect the updated test structures. However, they have a major problem: they are way too easy! The difficulty level on all of these practice tests does not even approach the difficulty level of the actual tests. This can give a student false confidence and leave him or her unprepared.
Aside from the practice tests, this is a decent book.
-Good vocabulary section, including root/prefix list with many examples
-100 Essential Math Concepts section serves as a great review tool
-Practice tests are far too easy
I would recommend this book to a 5th grader studying for the Lower Level ISEE or SSAT. It covers the basics and writes at a level accessible to 5th graders. However, keep in mind that the practice tests in here (even the Lower Level ones) are not a good reflection of the actual ISEE/SSAT. If you buy this book, be sure to supplement it with the official practice tests available from the ISEE and SSAT websites.
For 8th graders trying to do well on the ISEE/SSAT, the Princeton Review book, in conjunction with the official practice tests and a supplemental math workbook, is definitely the way to go.