Indeed, Venkatadhvari's 17th century Sanskrit work Raghava Yadaveeyam narrates the story of Ramayana (left-to-right) and Mahabharata (right-to-left) simultaneously.
there have been a number of simple examples in modern times -- poems that cycle through a pessimistic statement, a statement like "we will never see the day when", and an optimistic statement, and end with the line "now read from bottom to top" (which makes the middle line negate the pessimistic statement instead of the optimistic one.)
I always found those super tacky. I wonder if it'll get posted on Hacker News in the year 5015 as an example of brilliant 21st century poetry. I also wonder if Venkatadhvari's contemporaries found him to be tacky.
http://www.sanskritebooks.org/2009/09/raghava-yadaviyam-with...