Homestuck is a very popular webcomic that has been constantly updated since 2009. The comic is based around the adventures of four human teenagers and their session in the beta of a computer game called S-burb. The adventure begins with the introduction of the primary character, John Egbert, on his 13th birthday on April 13, 2009.
The reader is given a crash course on the style and asthetic of the rest of the series. Characters are often rendered humorously with no visible arms and overly large heads. Readers also learn how the story is conveyed, which is in the style of an early-90s adventure role-playing game. All narrated text is in a command oriented style, informing characters what they are to do and what actions to perform. Interactions between characters are handled differently than normal as well. Characters often converse in a chat client, sending messages and images as well as holding meaningful and long-winded conversations with each other. Characters rarely, until much later in the series, converse with actual spoken words.
When John begins playing S-burb, monsters called imps start materializing all around his house, and he has no choice but to attempt to defeat them. Additionally, there is a timer ticking down informing him of when an unspecified event is going to occur. Unbeknownst to John the timer is actually counting down to how long before a large meteor is going to smash into his location. Informed of this by his friend, Rose (via chat client), John and home barely escape through the medium to begin truly playing S-burb and find out the true meaning behind the game.
As of April 13, 2015, Homestuck has come off of hiatus and is resuming its regular updates. The story is very long and confusing but ultimately rewarding. If you are looking for a long but interesting read, the webcomic is available at mspaintadventures.com.