How to build html from multiple files?

Hi all:

    I'm learning to use the docbook. I've read some 
tutorials, most of them just tell me how to write the docbook xml files,
 but did not mention how to generate the final documents (html, 
pdf...etc). 

    for example, the Crash-course to DocBook povide its source, but i don't know how the build the html, the source structure look like this:

lyre@linux-4179e1:~/Desktop/
crash-course> tree
.
|-- en
|   |-- basic-notions.docbook
|   |-- bookinfo.docbook
|   |-- crash-course.docbook
|   |-- declaration.docbook
|   |-- duck.dsl

|   |-- emacs.docbook

|   |-- fdl-licence
|   |-- getting-started.docbook
|   |-- glossary.docbook
|   |-- graphics.docbook
|   |-- interface.docbook
|   |-- introduction.docbook
|   |-- licence.docbook
|   |-- links.docbook

|   |-- lists.docbook
|   |-- meta-information.docbook
|   |-- miscellaneous.docbook
|   |-- next.docbook
|   `-- tables.docbook
`-- images
    |-- duck.eps
    |-- duck.jpg
    |-- rectangles.eps

    `-- rectangles.png

I've tried the 'docbook2htm' & 'xsltproc' it mentioned, but they seems to work on only one file.

Thanks!