One can also use Google Drive to load books onto the N7 without attaching to your PC.
Place ebooks in a folder Google Drive. Install the Google Drive app on the N7 along with a copy of ES File Explorer. Using ES File Explorer open up from Local to net and you should see Google drive open it and then copy paste the ebooks wanted to your N7 ebook folder.
Some ereaders will actually load the book you want directly from Google drive using the Google Drive app. I use Coolreader and it doesn't seem to be able to do that but I read Aldiko does.