Thanks Krazy! I ended up just using the custom column approach. Having the correct syntax for searching has saved me though. In case anyone is following this thread: It's possible to have the custom column shown in the Tag Browser on the left. Once the it's shown and expanded (such that all your custom categories are shown), then you can just drag-n-drop books from the main window right to a category group. So that's nice. The info transfers via Calibre Companion to my Kindle Fire HD just fine. I'm using the paid version of CC... Not sure if that matters. Oddly, I decided to rename the custom column. It was "MyCats" but I renamed it to just "Categories." The new name has not propagated to CC, and there does't appear to be a way to actually rename it on the device. That's all. Thanks again.
