The open world design lets players freely roam Liberty City, consisting of three main islands, and the neighbouring state of Alderney, which is based on New Jersey.

[b] Two expansion packs were later released for the game, The Lost and Damned and The Ballad of Gay Tony, which both feature new plots that are interconnected with the main Grand Theft Auto IV storyline, and follow new protagonists.

Unlike previous entries, Grand Theft Auto IV lacked a strong cinematic influence, as the team attempted an original approach to the story.

[24] Niko Bellic, an Eastern European ex-soldier,[25] arrives in Liberty City aboard the cargo ship Platypus to escape his criminal past, pursue the American Dream, and search for the man who betrayed his unit to an ambush during a war ten years prior.

Reuniting with his cousin Roman, he discovers that his tales of riches were lies concealing his small, dirty apartment, unprofitable taxi company, gambling debts, and disputes with loan sharks.

Indifferent to Vlad's murder, Faustin releases them and employs Niko as a hitman, ordering him to kill the son of Russian crime lord Kenny Petrović.

While working for the Irish Mob, Niko befriends gangster Patrick "Packie" McReary, helping him and his brothers carry out various jobs, including a major bank robbery.

[37] Producer Leslie Benzies estimated that the budget of the development efforts exceeded US$100 million, making Grand Theft Auto IV one of the most expensive video games ever made.

[39] Art director Aaron Garbut said that the team chose the setting because of the detail and variety it provided, describing New York as "an amazing, diverse, vibrant, cinematic city".

[40] Writer Dan Houser added that the team "wanted to be somewhere where we had a foothold" due to the amount of research required for the world; Rockstar Games's main headquarters are located in New York.

[41] The team consciously avoided a precise recreation of New York City to allow for more enjoyable game design,[32] selecting the areas that they felt "characterised it the best".

[42] To achieve a realistic environment, 60–70 employees from Rockstar North travelled to New York for research: first at the beginning of the project in March or April 2005 for a week and a half,[39] and a smaller trip in 2007.

When deciding on Niko's background, the writers felt that being an immigrant could lead to more dangerous situations, and therefore more enjoyable missions; after discussions with criminal experts, Dan Houser found that "the real scary characters are not born in America anymore".

Dan Houser felt that the missions in San Andreas had become too linear, and wanted to present choices to the player in Grand Theft Auto IV.

[38] The team based the ethnicities, clothing, and behaviours of the NPCs on the photographs and videos that they captured around New York, divided into different areas;[40] they created mood boards for each location.

[57] For the gameplay and animations, the team redid a lot of the work from previous games, wanting Grand Theft Auto IV to "feel next-generation".

[40] The role-playing elements from San Andreas were removed fairly early in development, partly due to the animation work it would have required, and because consistently needing to visit the gym felt antithetical to Niko's motivations.

Image Metrics head of production David Barton noted that "having realistic eyes is 90 percent of the battle", as it allows the player to believe the character.

"[59] The developers contacted over 2,000 people to obtain recording and publishing rights;[60] they hired a private investigator to locate the relatives of late Skatt Bros. member Sean Delaney to license the band's song, "Walk the Night".

It was narrated by protagonist Niko, and depicts the open world accompanied by the song "Pruit-Igoe" by Philip Glass, originally composed for Godfrey Reggio's 1982 documentary film Koyaanisqatsi.

The trailer features the song "King Ring" by Russian rap artist Seryoga, which Rockstar felt captured the "melting pot mentality" of Liberty City.

[12] Hicks of Official Xbox Magazine and Andy Robinson of Computer and Video Games both called Niko "charismatic" and "likeable", stating that they prefer him over previous protagonists of the series.

[115] David McComb of Empire called the combat "sharp and instinctive",[124] and Hicks of Official Xbox Magazine felt that the cover system allows players to execute an attack plan.

[115] Giant Bomb's Gerstmann and GameRevolution's Costantino felt divided about the multiplayer, the latter naming it a "fantastic idea", but feeling as though connectivity problems resulted in a "broken" experience.

[131][133] The addition of the Video Editor was met with positive reactions; GameSpot's Calvert called it "a great way to get creative",[1] while Kieron Gillen of Eurogamer criticised the unpredictability in its timing.

[129] Critics also praised the addition of the customisable radio station, which allows players to listen to their own choice of music; Tom Chick of 1UP.com named it the best feature of the port,[127] and Steven Hopper of GameZone called it a "great touch".

[179] In 2007, then-Florida lawyer Jack Thompson, known for his campaigns against the series, stated he would take measures to prevent the sale of Grand Theft Auto IV to minors.

[183] Thompson responded by filing a countersuit accusing Take-Two of violating federal RICO statutes, committing perjury and obstruction of justice, and conspiring to deprive him of his civil rights.

[181] On 18 September 2007, Thompson filed a document with a federal court in Florida, claiming the assassination target of a mission in Grand Theft Auto IV is a lawyer character based upon himself.

[196] In August 2013, 87-year-old Marie Smothers was killed in Slaughter, Louisiana, when her eight-year-old grandson shot her in the head with a handgun after playing Grand Theft Auto IV; under state law, the boy could not be charged for her death due to his age.