More Nexus Than Human

Got me a nice used Nexus 7 today.
32 GB, WiFi only.
Haven't played that much yet, but got a few apps as well a bunch of files in there already.
First app was Kindle, followed by Last.fm and last, but not least, specially when it comes to getting my own ebooks to show on the Kindle app, the ES File Explorer File Manager.
To mount the Nexus 7 on the Linux lappie, the instructions here How do I connect a Nexus 7 to transfer files?, but even after mounting the Nexus, I wasn't able to reach the "kindle" directory -to copy my .mobi files- on the root of the Nexus' file system.