Allow ability to download multiple books locally on mobile

For mobile readers the process to get books downloaded for offline reading is to individually select them and download, either by tapping the book and choosing the download option or tapping the download icon that's visible on the cover from the bookshelf view. Since this only allows for one-at-a-time downloads, some users have requested the ability to select more books for a simultaenous download to their device.  Right now we see this as having two clear options for how to solve for the requested functionality.

1. On virtual bookshelves, give a "download all" option in the Android and iOS mobile apps. This would allow readers to put books into a specific shelf, then open it on their mobile device and download them all at once instead of selecting each one individually.

2. Have a dedicated "Mobile Sync" virtual bookshelf, where any books added to it will automatically queue up to download when your mobile app is opened while an internet connection is present. This would allow you to add the books easily while on the website, then when you open the mobile app it will see which ones aren't already local and download the rest.

We'd love to hear from the community on your thoughts. Do you see this as a useful feature? Which of the above do you think sounds best, or do you have another idea entirely? We'd love to see some discussion around this. :)