[tomsem]

The Manage Content page has been this way for awhile now. It's actually better than it used to be for many purposes (has more features).

As for Collection management, the best way might be to use one of the mobile apps (iOS or Android) to do this. You can select many books at once, the list is as long as your library, etc.

That said, the implementation does not scale up well for use cases like 'author' or 'genre' collections, and there is no way tag things with calibre and have Kindle do anything with this (short of jail breaking anyway).

It works okay if you have a relatively small number of Collections and apply these to a limited subset of books, e.g. 'Started', 'Read Next', 'Favorites' etc., which is how I use them.

One might want the ability to add Subject or Series info to the ebook metadata (or in some well-defined metadata companion file that you could edit) and have Kindle platform do something with it, but this feature does not exist.

Pocketbook allows browsing by Genre, Series, Author, and lets you browse by Folder as well, but I haven't explored mine enough to know how much control you have over that (i.e. how to leverage it for ebooks you side-load using Calibre). You can also create collections but it seems to me no better or worse than what Kindle platform does.

Personally I am not much for 'organizing' and have no issues with finding things using Search or Sort. I only use Collections to bring some focus to some of the books in my Kindle library, again, the ones I've started reading, and ones which I stumble over and want to give higher priority to when I'm finished with a book and am ready to start another. Grouping by Subject/Genre would have very little value to me, if it required me to come up with my own system.

It'd be kinda neat if something like a LoC or Dewey Decimal classification could be applied and you could browse things on your reading device (or online bookstore) the way you would in a physical library (as organized by professional librarians), but I've never seen that implemented for consumer oriented ebook reading platforms. I used to have favorite LoC/DD numbers that I would head for when visiting new libraries but am afraid those brain cells have been reassigned, as it has been many years since I've spent any time in a public or university library. At least for non-fiction subjects, it really helped browsing a physical library efficiently: I could walk into any library and quickly see what was available in my areas of interest with those magic codes.