Walmart offers the Mainstays 31″ 3-Shelf Standard Bookcase 2-Pack in Rustic Oak for $19.98. Choose in-store pickup to dodge the $5.99 shipping fee. That’s $17 off and the lowest price we could find. (For further comparison, we saw a single unit for $14 last week.) Each one measures 31.7″ x 29.7″ x 11.7″.