extension

EPUB (electronic publication) is a widely used and appreciated e-book standard, file type maneuverable by numerous and numerous applications, operating systems and devices.

Via Ubuntu Software Center (and/or PPAs) users can install Calibre (a powerful e-book library management tool with in-depth file-conversion capabilities, including EPUB) and Sigil (a versatile EPUB editor with a multitude of functionalities).

LibreOffice is a powerful office suite that features built-in full-fledged tools, such as Impress, Draw, Calc, Writer, etc, tools with a specific functionality, that allow users to express documents, presentations, drawing, mathematical equations, etc via a "complete" office center, from where appropriate/needed "directions" are to be used.

Users across the internets are reading books in numerous standards like PDF, MOBI, LIT, etc, nevertheless one of the most commonly used is EPUB (electronic publication), a free and open e-book standard.

Writer2ePub is an extension useful to create EPUB files from various filetypes that can be opened with LibreOffice Writer (DOC, RTF, etc), meaning the extension easily creates various files to EPUB from inside LibreOffice.

LibreOffice is the new default office suite in Ubuntu and, although has support for extension, there hasn't been a public place to gather this extensions in a Firefox-like approach until now.

Notify-OSD is the default notification framework in Ubuntu, smooth, sexy, but doesn't support everything out-of-the-box. What I mean is that important things, like browser messages, are left behind.
Chromify-OSD is an extension that uses notify-osd notification framework in order to deliver notifications in Chrome/ium.

Install it via Chrome Web Store by searching "Chromify-OSD" or grab it from here.