Your 6.6 expertise is not useless. The version 8 GUI has improved remarkably and there are new and improved features relative to 6.6 but the fundamentals are similar, so your 6.6 experience remains valuable. You will probably find the book useful mainly for its walk-throughs on getting the best out of the various tools, and for guidance on integrated workflows between SilverFast and Adobe photo editing applications - what is best to do where. But with the experience you've accumulated you should find a fair amount in that book quite familiar if under a new and improved guise.