Here in Norway you definitely have to go by way of the library app,
ebokbib. I don't think there's any ADE component there, presumably to keep costs down.
It works sort of OK, except for the reading experience, which is marred by the lack of a TOC and support for hyperlinks. I've succeded in side-loading the app on a Sony PRS-T1, but the flickering caused by side-change animations etc. was so annoying I couldn't be bothered to use it on that device.
I do wish the ereader producers would start to allow third-party apps on eink-devices.