I understand. Still, since I have a lot of interactions, KF8 is irrelevant. I'm not interested in the "regular" kindle devices, only in the Kindle Fire, which is practically an Android device. In that case - what should I upload?

Is it the same as google play store?
Which binary should I upload: "Ad Hoc Distribution" or "Google Play Store" distribution?
thanks,
Ranco

Sure, that's what I meant.
BTW, I found a way to do it in Java, but not Javascript:
getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

Many games do keep the screen on at all times. see Candy Crash for example. Obviously, it consumes a lot of power, but at least for a self-reading book it makes sense (to me).

There's a nice shortcut, though. you don't need to drag new image objects to the stage and then place an image in it for each of your images. You can simply drag all your images from the assets tab into the stage (but not onto an existing object) and a new objects will automatically be created for each image. Then, it is just a matter of placing the objects in their location, and sorting the layers (drag/drop). Very easy. I built a 16 pages interactive children's book in 3 days, with dozens of elements (images, animations and audio).
Ranco

There must be an option (if there is, I can't find it...) to keep the screen on. A book is usually read aloud by a narrator, the kids listen and might not touch the screen for a while. Then, suddenly, the screen turns off, and when awaken (by one of the parents...), the page reloads and narrations starts over from the beginning. This is a big issue, in my eyes.
If there's a way around that, please advise.

Great, thanks! I want to release my book to the app stores this week, when is the next release planned?

is there a way to publish my book on MS app store (for Windows phones) as well as on apple and google play?

Moreover, even if I set the 2nd Android to 1920x1080 and install it on an LG G3 (2560x1440), I see that the selected resolution is 1280x800, which doesn't make sense at all: the correct aspect ratio AND the closest resolution is 1920x1080 !

Giancarlo, I've tested what you've wrote, and what I see is that the selected workspace (per OS) is the one with the closest height and/or width, but not the one that "better suit the device screen proportion".
For example:
I have 2 workspaces for Android: 1280x800 (w/h = 1.6) and 640x360 (w/h = 1.777 = 16x9). When creating the second workspace, I selected page size 640x360 (defined as "Android 5" in the drop-down menu) assuming the proportion has priority over size (640x360 = 16x9).
However, when I installed it on my LG G3 (screen resolution 2560x1440), the workspace that was selected is 1280x800, with 16x10 aspect ration, as oppose to the correct 16x9 aspect ratio one.
See phone screenshot here:
link
What an I doing wrong?
Thanks
Ranco

Tried it and it works great, thanks a lot!