If you use it as a java reference it will not be that useful, because it will cover just a few (small) topics about new changes in Java 7 (like diamond syntax, String in switches, underscore in numbers, boolean literals,...). Because that's what you need to know for the OCAJP7 exam. The big topics (automatic resource management, multi-catch, nio 2.0,...) will only be on the OCPJP7 exam, so these topics will be covered in a book dedicated to that exam.
I won't recommend usage of a certification guide as a reference book. Java 7 includes many language enhancements that are neither covered by the 'OCA Java SE 7 Programmer' or 'OCP Java SE 7 Programmer' certification. You can access the complete list here.
For an example, new features in Swing aren't covered by any of the above mentioned certifications. It wouldn't make sense for a certification book to cover topics that aren't covered by the relevant exam.
Also, a certification book will define techniques, approach, tips, sample questions etc. to prepare you for the exam, which are not needed in a reference book.
Thank you both for your replies. I will try for an alternative book which is appropriate for JAVA 7 reference. I also work in swings and i never heard before it has new features in JAVA 7. Thanks for letting me know Mala.