Version 1.5.2 is a major bugfix release by and large. New features:
* Full XHTML compliance if you want (however with MathML you don't
* New <blockquote> und <quote> elements in the DTD with tha same
meaning as in DocBook and HTML.
* Many additionally supported Unicode symbols.
From the Sourceforge summary:
tbook is a system that typesets XML documents with high-level LaTeX
while HTML, XHTML+MathML and DocBook output are equally
possible. It bases on the LaTeX-like tbook DTD developed for this
project, XSLT transformations and further tools.
All transformations work with bibliography, index, formulae, and
graphics. Therefore the transformation processes include some complex
tasks (e.g. generating of bitmaps for all formulae) which are greatly
simplified by shell scripts that are automatically generated.
The LaTeX output is also suitable for pdfLaTeX and uses its features.
For equations, you may use an almost-LaTeX syntax; except for complex
cases, you don't have to type MathML directly. (Instead, it is
transformed to that eventually.)