These misleading terms Adaptive and Responsive don't matter much, but rather the result which is an experience of the user (and higher conversion rates) across various platforms (including operating systems, browsers and screen resolutions). For authors and publishers (both book and web formats), design is a rather important topic. Hardcover, paperback, ebook, web are physical/digital format issues (not to mention pricing/paywall discussions). But the real question is does the content (information) and how it is presented (design) change based on device, platform, or screen resolution.
What Matters in Adaptive and Responsive Design
We at Parliament Press have a slightly different take. First, we need to clearly understand what decisions need to be made, and what changes to implement, and finally, how to really think about device proliferation and ubiquity.
Design Complementary Experiences
Complementary experiences can indeed be identical. But they should at the least inform each other. Recall with experiences we want to reinforce and enhance a brand. Therefore do not contradict expectations which one platform has created. A big example of this is the fragmentary and contradictory experience for Bloomberg apps and website. It is obvious that entirely different teams created these various apps and they likely took as a goal the desire to not duplicate or even enhance what one platform provides in terms of navigation, interface, and information.
Start with a Single Design for All Platforms
The exercise of designing for all platforms makes it abundantly clear where the boundaries of usability and information consumption is. Tradeoffs should be made to provide a reasonable experience at the smaller mobile screen sizes, while having a reasonable experience at the most common desktop display sizes. Mobile should have the slight preference here, since it is the growth platform. This will also help make less is more decisions on removing clutter from the interface.
Look at how the different platforms in terms of operating system, browser and screen resolution are consuming the content, then take that as the point of departure for special design, however implemented, for different platforms.
Client-side vs. Server-side Customization
Multi-platform Design (MPD)
The words Responsive and Adaptive should in all cases be eschewed for a category that is descriptive to its end goal, that is multi-platform. And because three letter acronyms are all the rage, we can call this MPD. In discussing MPD, we don't actually focus on this, but rather use the language of mobile. Not mobile first but rather mobile friendly. If a site is mobile friendly, visitors can achieve their goals in the same way as on another platform (desktop/laptop). That is the first step toward multi-platform design. Second is having a feedback loop of mobile friendliness into the design in general. What happens in this process is that design elements and constraints shift from being one platform, then another platform, then a third platform, to that of multi-platform-ness.
See the most recent post on Mobile Web Best Practices