Its a tough test, I personally thought it and CIT were the two toughest of the CCNP exams and I'll debate that with anyone.
Everything you need is in the Cisco Press Exam certification guide but it may not be as detailed as you need to trully understand the concepts. My advice is to really study the concets in the book and re-inforce it with information that can be found on CCO. For example, lets take ISDN call setup and teardown. Do you understand all of the steps associated with it and can you take a look at a debug from it and tell us what every line means? If you can't, don't take the test yet. The same goes for IPSEC, Frame-relay, DDR, etc.
Its a detailed orieted test that requires a lot of analyzing.