I probably shouldn't be the one saying it, but, of the dedicated e-ink ereaders, Kobo ereaders are the best for use with calibre. The reasons include:
- Series support.
- Collection management.
- Plugin support for getting status from the device.
- Annotations plugin support.
- Metadata updating on the device.
- Plenty of people here if you need help.
On the ereader, series info is treated well. Series info is displayed as a separate line in the book details and in book lists, the lists can be sorted by series and there is a separate series list. And searching for books includes the series name.