In production terms, the publishers seem to have done an excellent job. XSLT
and XPath are now back in one book, and although this is now over 1300
pages, the paper quality and binding are much better than the 3rd edition,
and the book is no thicker or heavier than the 900-page XSLT volume of the
3rd edition.

about it falling apart; hopefully the hard cover format will make this less
likely in future. The publishers have also fixed all the frequently-reported
problems in the previous edition: the diagrams are much improved, there is a
vastly better index, and above all the alphabetically-organized chapters now
have running page headers that tell you where you are in the chapter.

The changes to the content are largely (a) to bring XSLT and XPath back
together into one volume, (b) to bring the content up-to-date with the final
W3C specifications of January 2007, (c) miscellaneous updating of product
information, etc, and (d) correction of errors.

--
Dave Pawson
XSLT XSL-FO FAQ.
http://www.dpawson.co.uk