Put your Kindle in landscape mode.
Note where you are at = that setting is only available while viewing a document.
Tap the 'top' to bring back the menu bar.
Tap the 'home' icon (without changing the settings).
See? Now the display is in portrait mode.
Translation:
The "landscape" setting appears to be a feature of the document reader application, not of the graphic display stack (ah, mostly the 'framework' part of it).
And if you play with it a bit more, you find that the portrait / landscape setting is not "per book" - it affects anything the default reader handles and only what the default reader handles.
- - - - -
There is a way to put the hardware to sleep, without changing what is displayed on the screen.
but that would probably be tricky to program -
It would have to display the "book's page" in the reader that has the desired, landscape, image as a page and then signal the kernel's power control to immediate enter sleep state (so the framework never executes to put everything back to portrait).
And you can almost bet that once that is made to work with one specific device/firmware version - Amazon would release an update that would break it.
