How do you mend a broken shelf?

I had to clear out my bottom shelf this morning. Last night I awoke to a loud clatter as my books and CDs fell from the shelf, but I was too lazy to get up and examine the damage, so I just stirred and went back to sleep. I thought maybe something hit some other thing and everything dominoed.



It turns out that the shelf gave way, no doubt under the weight of the new semester's textbooks. I'm no carpenter, but that doesn't look good. :(