I never worked with one. So, I wonder if they are for real when it comes to really producing a working system. How effective/how efficient are the end products where they are a part. Just wondering. Kishore.
Typical design book authors have almost always more than 10 years of industry experience. In that sense, no, they're not "hype". Regarding the quality of their projects' outcome, please remember that raw performance should most often be second to maintainability. Design patterns and OOD principles are generally oriented towards maintainability, not performance.
The design principles and techniques in those books aren't specific to the author, but are already discussed and in use in a big part of the community. And you typically become a respected author by being able to resonate with (at least part of) the community.
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus