A friend of mine is going to write a book. Therefore he is looking for an easy WYSIWYG solution. First I recommended latex, but this would be a bit to hard to learn. A big part of the book is finished and saved in a odt-format but for the publishing he has to offer more "powerful" formats (latex, xslt, ..). We tried the following:

 - Latex - LyX: Ok, lyx is great, but it was a bit too complicated and we had to fight against bugs.
 - Markdown (with latex export) : The book will contain a lot of tables (big ones) and so it wouldn't be the best experience.
 - Libre Office: There are latex export tools, but they're very bad.

The best solution (by now) is Sigil (ePub-format) - but tables are not supported yet.

So I am looking for a format and a good wysiwyg editor. Only a few functions are needed (heading, bold, kursiv, underline, tables and picture integration).