One very good solution is Calibre Companion;
https://play.google.com/store/apps/d...calibreandroid. This will connect via WiFi to current versions of Calibre as opposed to USB.
But are you sure that Calibre is not recognizing it? Calibre does (in current version 0.9.12) support MTP mode for USB connection...
I just attached my wife's Arc; it's still installing the drivers on my PC; sigh, but on the ARC I do see the option for either MTP or PTP mode.