Some features (there are thousands of them):
- You can make plugin for any magazine (python) including self-published
- You can scan books for ISBNs and get certain 1 on 1 match online without any effort or search foo. Without ISBN it will search by given criteria
- Batch operations for everything
- It first uses cover of the book (first page in PDF, epub etc), downloads covers if there aren't any, or generates them if nothing can be found
- You can add arbitrary metadata and give them types (bool, text, urls...)
- You can share via web server and access lib from browser and even add books from browser or simply copy them to special folder
- Its x-platform
- It supports zillion formats, and basically you can add zip or anything. Audiobooks could be handled better but ok.
- Its updated weekly for years
- You can have different libraries, groups, virtual libs etc.
- Awesome converter from-to number of formats
- You can both have online tags applied and your own tags. I have personal tags such as `reading`, `must read` etc. along with my own classification on books that isn't merged with online stuff and is kept separatelly.
- Awesome ebook reader
- Many more options
- There are plugins to put kindle encrypted books offline !
Simply, there isn't anything better out there. Anybody not using it simply doesn't know better.
The only thing it doesn't have is in text search, but hey... I am sure its comming one day or you can implement samo mumbo-jumbo on your own.
NOTE: Calibre is IMO not that good for research papers although YMMV. Zotero might be better choice for this.