Those of you who have written books and long articles in the past know too well about the importance of keeping your writing environment as distraction free as possible. That very much applies even if you are writing your book online. Manifest for WordPress is a free but super clean theme just for authors. It does not have too many bells and whistles but makes writing your books a whole lot of fun.
Manifest does not have any sidebars and widgets. It has a 500 pixels wide layout. The typography is quite excellent. This theme does support WordPress gallery. It can handle sub-pages too. Posts are marked up using hAtom microformat, which is quite nice to see.
Manifest does have 404 page and archive templates. It does not have too many advanced features but is great for authors to get started with writing or sharing their book online.