Just be aware that the collections are virtual they do not create any physical organization on the device whether you create them on the device or via calibre.. if using calibre just be careful as each tag you create in calibre will generate a collection on the device.. personally I find it much easier to create manage and populate the collections on the device.. of course it deepens on how many books you add at one time.. I currently have a 1000 + books organized into 92 collections.. by author as it happens