Today, the Shahnameh is praised as being a hallmark of traditional Iranian culture, its "national epic." Nationalists in the early 20th century used its message to push forth a unified country. Interestingly though, Ferdowsi was not recognized during his life for the epic he wrote. Ironically, it was only after his death that people saw the significance of the work. Ferdowsi was originally buried in Tus, the city he was born in. Reza Shah, progenitor of the Pahlavi dynasty, saw the intrinsic value of the Shahnameh and what it could be used for and built a tomb befitting the great author in his home city of Tus. The tomb itself is based heavily on traditional Persian architecture, in honor of the culture Ferdowsi helped immortalize. “I am deathless, I am the eternal Lord, for I have spread the seed of the Word,” sums up his impact.
A lot of the works we have read certainly had an impact on other writings of their times, as you can see the same motifs and themes popping up from Gilgamesh to the Iliad to Beowulf. Ferdowsi's tomb shows that the impact of a story can not only transcend time, but that it doesn't have to impact other writers. An entire country was able to find a sense of unity with his story, and that's a powerful example of the overall impact of literature.