Scribus is a maturing publishing tool which has much to like. The upcoming (when? who knows?) release of 1.6 should put it squarely in direct competition with Adobe Indesign, it's proprietary competitor. Scribus is free and open source software, developed with love. However, there is one bad part which is the development lead who believes that new versions (e.g., 1.6) should be released over several years, rather than several months. Too slow for my tastes, though they are doing incremental releases at a faster rate, and frankly it is a nice piece of 'ware.
> Note, my own use of Scribus fell down with several issues, including this bug that may not be around anymore, and I've gone back to an older approach using Inkscape for vector graphics and Markdown, Pandoc, and XeLaTeX (XeTeX + LaTeX, which handles unicode fonts and is the only real solution for non-latin script support) to generate epub and pdf programmatically.
Scribus is basically damned awesome and should be tried out. It is the future (and possibly current) replacement to Adobe Indesign. Along with GIMP, Inkscape and Blender, Adobe can be retired (and I personally have not used any of their software since 2010 (and any Microsoft software since 2007).