September is National Library Card Sign-Up Month. Even if you don’t think you will use your library card (you will), it is a great way to show support for your local public library (it needs it).
And like all causes that people are passionate about, the use of libraries has inspired some fantastic art. Ann Leonard, a librarian at the Pinal County Library District (AZ) created a series of promotional images celebrating the benefits of owning a library card in the style of classic Penguin paperback covers. This is my favorite:

There is also one featuring a DNA double-helix. I was happy to note that it is correctly pictured as a right-handed double-helix, but it is a bit too elongated to my pedantic eye to be my favorite as one might expect. Frankly, you are spoiled for choice.
*Hat tip to Cory Doctorow at BoingBoing.