It has been announced through Twitter that Metro: Last Light will be slightly delayed towards May 14 for North America and May 17 for the rest of the world.

The original source can be seen here and 4A Games explains that the extra time is required to polish the game up better. Also from the press release they have stated:

"The new release date is the ideal way to strike the balance between bringing the best out of Metro: Last Light and not keep the fans waiting longer than necessary." said Dr. Klemens Kundratitz, CEO of Koch Media. "We won't leave that time unexploited and will work closely together with 4A Games to make the game even better. It will receive all the attention it deserves."

Metro: Last Light was written by Dmitry Glukhovsky, the author behind the original novel Metro 2033, which inspired the creation of the video game with the same title. The Metro 2033 and 2034 novels have sold over 2 million copies worldwide and this year his latest novel Metro 2035 will be available outside of Russia.

The story places the character in the feet of Artyom, as whom they will have to strive to become the last light for all mankind; fighting for survival against hordes of mutants and other factions within the Metro tunnels of Moscow.