One of the problems with writing ebooks in XHTML (we're all using
XHTML, aren't we?) is the lack of good writing tools that support it
as a format. Well, there's a new tool available, Nvu, which does a
pretty good job of being a freeware XHTML editor. It supports
stylesheets and templates, and lets you work in either HTML or XHTML.

It's not close to being Mellel -- which I'd highly recommend if you
are an author writing on a Mac, and which demonstrates nicely the
advantages you get by developing for MacOS -- but Mellel doesn't
export to XHTML, and really doesn't support ebooks.

One nice thing about Nvu is that it's built on the Mozilla framework,
so that you can add Mozilla/Firefox-style extensions. Of course, most
browser extensions won't be useful for Nvu, but the facility will
allow extension-makers to provide more functionality incrementally.

http://nvu.com/.

Bill