Originally Posted by ApK
You might want to double check, as I believe this is the way the Kindle Android app works regardless of device.
You should have an "/sdcard" path on any android device, and you should see a kindle folder directly under it, and the app can SUPPOSEDLY find books there as well as in the system data folder you mentioned earlier.
Note that /sdcard does not NECESSARILY refer to the ACTUAL external SD card (on my wife's phone, the actual card is mounted as "/SDCARD/_ExternalSDCard") and the app only works for files in the /sdcard/kindle location.
That being said, my attempts to sideload to that folder on my wife's phone were inconsistent. Sometimes books would show up, sometimes they wouldn't, so I decided it was easier just to use the Kindle app for Amazon server based books and put another reader app on for sideloaded stuff. Honestly I'm not crazy about the import process for Aldiko either....
My tablet does its USB connection via MTP, so what I see is not a "raw" mounted drive. When I look at Windows Explorer, I see a device called "GT-P3110", which is listed as a "Portable Device", and does not have a drive letter. When I open that, I see two drives: "Tablet" (the internal storage) and "Card" (the SD card), again with no drive letters.
When I use the file explorer on the tablet itself, then it's as you say: root, with "sdcard" and "extSdCard" below it, and "sdcard" has a "kindle" folder in it. But that's internal storage, not the external SD card, so I'm no further forward
EDIT: You're right - putting books into "Tablet\kindle" (which is the same as "sdcard/kindle") works fine. But, again, that's internal storage.