... Do you want to have a nice Christmas mood, without endangering the local fauna and flora?
... Wouldn't be nice to have a Christmas tree that shows your love for nature and knowledge?
... Do you have a big collection of books stashed away somewhere, collecting dust?

Your problems are solved! Now you can do your own Bibliophile's Christmas Tree!
(inspired by http://scarletrune.tumblr.com/post/14055291117/a-bibliophiles-christmas-tree)

So, clear up some floor space, put some nice Jazz music to give that extra Christmas mood, and lets start!

Step 1: Collect and Pile the Books by Size

Go around the house and collect as many books as you can find, with all sizes and dimensions. Don't underestimate the power of a book :) as for my tree, I had around 100 books of all sizes to make a 1m (3 feet) book tree.

After you have them all close by, sort them by its dimensions (thickness, width and height) and make book piles of similar size, like on the picture.

Step 2: Create the Tree Base

Now that you have all your books nicely ordered, you have to quickly plan how big your tree will be.
We did not have many books (around 100), so we created a triangular base, using the widest and largest books available, but you can start with a square or wider base, if more books are available.

As you can see in the picture, pile the books in a triangular mode, so that each layer has the same altitude to the other books (add more than one book when necessary to have a symmetrical layer), and shifting the books so that they don't look like a wall, but look like tree leaves.

We decided to leave the titles of the books facing outwards, to give more color and display the books we have :)

Step 3: Pile 'Em Up!

Now that you have a solid base, keep piling your books, following the same pattern as before: solid layers, keeping the height similar, but now try to use smaller and smaller books for each layer.

Step 4: Finish the Tree Top

When you are almost running out of books, it's time to finish the tree top.
For that, you can use your creativity, using smaller pocket books, or different layer organizations, until you are left with your tiniest book on top.

Step 5: Decorate As You Like!

Here you have, the Hundred Books Christmas Tree! Feel free to add Christmas lights (beware of fire hazard).

We decided to decorate the tree with Crochet Christmas Balls (instructable coming soon) and custom Christmas wall paper decorations.

Feel free to post your own Book Christmas Tree on the comments!