Question: Is there an alternative tool similar to [MS Reader](http://www.microsoft.com/reader) that allows one to both **publish** and **view** ebooks in Linux, Mac and Win?

Answer: 
That entirely depends on the format you prefer, if you want to open Microsoft's proprietary LIT format and various platform, then Calibre (as per Mavrik's suggestion) is your best bet.

If you're willing to settle for **.txt, .doc, .html, .fb2** or **.rtf** formats then i suggest Cool Reader. [Version 3](http://coolreader.org/crengine.htm) is a cross-platform (Linux, Mac and Windows) open source E-Book viewer.

![alt text](https://i.stack.imgur.com/DFysF.jpg)

**[Cool Reader 2](http://www.coolreader.org/e-index.htm)** is my personal favorite, but version 2 only works for the Windows platform, unlike version 3 it supports skinning, text-to-speech and MP3 export.

![alt text](https://i.stack.imgur.com/Hsf0z.jpg)

*Cool Reader 2 is closed source, but free and portable.*

*Don't mind the Russian screen shots, despite its origin, the software is all in English. :)*
Just save your files as PDF. That's the most cross-platform you'll get (all OS + all phones, handhelds and web)