At the moment, that book is the best you are going to get for covering both. What I wrote about using that book in my blog
If you are planning to take the OCP afterwards and don’t mind the material being mixed together, this is a great resource. If you want to get your OCA first without being exposed to the OCP information, it isn’t helpful though. Also, some of the content is no longer on the exam so you have to ignore these parts.
When OCPJP 7 books start coming out, there will be a book with all the materials. For now you have to learn the Java 7 parts outside of a cert book.
You have to take one $300 upgrade exam. (Which makes the cost the same as starting with OCAJP 7. The big difference is you get a professional level certification sooner rather than an entry one. And that you don't have to upgrade to 7. 6 is a valid cert to hold.)