I have the book. I bought it a long time ago, when CMP 2.0 just came out. I've read it cover to cover (which is why HFEJB can be a little slow at times, no offense). But this was a long time ago, and I didn't have any EJB projects to work on at the time so it and my memory languished.
I haven't taken the exam, but I will say this about the book Mastering EJB: it has very few real app server examples. And the few examples it does have are for BEA Weblogic. Dealing with BEA's expireware server is not fun, either, unless you're unemployed and plan to scream through the book in a couple of weeks. Therefore, getting the examples to work with, say JBoss, is quite a trying experience.
Other than that, it's a really good book. Covers everything.