I’ve posted a copy of the sample book here:

http://kevin.godby.org/latex/sample-book.pdf

Keep in mind it’s a work in progress. The next steps are:

1. Finish creating the sample book with all of the elements from Beautiful Evidence.
2. Abstract the useful elements to the tufte-book class.
3. Abstract the common elements from the tufte-handout and tufte-book classes into a tufte-common file.
4. Clean up the code and fix bugs.

At least, that’s the plan!

Thanks for your comment.

What kind of justification/centering are you looking for?

If you use the “justified” option, it will set all the text fully justified—that is, the text will be set flush with both the left and right margins:

\documentclass[justified]{tufte-handout}

Also, note that the main textblock will always be off-center on the page. This is to provide a wide margin for sidenotes.

If I misunderstood your question, please rephrase it and I’ll try again.

You can also get support from a wider group of people through the Tufte-LaTEX mailing list.