Hi and welcome to mobileread
I almost missed your question since it's in a very old thread from 2007.
A quick answer to your question is no - you cannot mark books off as read.
Most people either delete books from the Kindle once read (any you've got from Amazon can still be downloaded again) OR file them away into a "Read" or "Completed" collection.
A 'collection' can help to organise the books you have on your Kindle. They work a bit like folders on a computer although they are technically not folders but actually labels which are assigned to each book. For instance, I have a collection called 'Reading Now' which is where (you probably guessed) I store all the books I'm currently reading. It's a way of grouping books together.
To set up a collection on your Kindle, make sure you're on the Home page (press the Home button) then press Menu and select Create New Collection. Give your collection a name and click on Save.
If your collection seems to have disappeared then click right up to the top of the screen on your 5-way controller, click to the right and select Collections. This will now display all your collections before any book titles.
There are various ways to add books into a collection. You can select a book, click right on the square 5-way controller button and choose Add to Collection. Or you can select a collection, press Menu, choose Add/Remove items and organise multiple books. Tip - while using the latter method, press the Menu button again to Add all the Items on This Page. This is a very fast way to organise your books.
OR if you want to know how to delete books refer to:
http://www.kinworm.com/2011/02/q-12-...om-kindle.html