Whether it was The Larry Sanders Show or The Sopranos, HBO (a subsidiary of Time Warner (TWX)) has offered original programming that is always a topic of discussion. Today, its biggest "it" show is Game of Thrones. As the fantasy drama prepares for its fourth season finale tonight, it's not hard to see why it's so successful and just what it means for the cable giant's business.

Credit: HBO

By the book

Game of Thrones is based on the book series "A Song of Fire & Ice" by George R.R. Martin and is comprised of seven novels (though the final two remain unfinished). It has everything you'd expect in a fantasy series including dragons, magic, and epic wars; naturally audiences were quick to embrace it.

For HBO bringing these elements to life presented executives with a challenge, namely doing it justice without breaking the bank. Enter the show's executive producers David Benioff and D.B. Weiss who worked closely with Martin to find ways to seamlessly and realistically tell the story of the seven kingdoms as weekly episodic series.

What the trio ultimately developed is special both because of how well it's produced and because it's brutally honest to Martin's original novels -- even if the story dictates the exit of a popular character (or 10). To the network's credit, executives have not stepped in even when one of the departing characters was prominently displayed in the show's marketing materials.

That's a rarity in today's television landscape as losing a main "face" of your show so early (and so often) is rarely done -- the financial implications could be disastrous if fans tune out.

King's ratings

Credit: HBO

Perhaps the most amazing thing about Thrones is that its audience is still shocked on a weekly basis. This season raised the stakes and the majority of the episodes could have been near season-enders themselves. Like network sibling True Detective, which got off to a banner start in 2014, Thrones came in above expectations in the ratings. Combined the two shows helped boost the channel's earning power, which in turn led to increased first quarter financials for parent company Time Warner.

Thrones now averages 18.2 million viewers a week (with all viewing methods combined) and has three times this year matched its highest individual (live) rating with its season premiere even crashing the network's HBO GO mobile viewing app. What's impressive is that the show didn't initially pull in these kind of numbers -- it opened in 2011 to just 2.2 million viewers (live) and has grown ever since to become what is now HBO's most popular series of all time; displacing former record holder The Sopranos, which had 18.2 million. With True Blood, Boardwalk Empire, and The Newsroom ready to wrap in 2014, having a consistent ratings juggernaut like Game is of the upmost importance.

'Game' of gold

Credit: HBO

The massive pop culture success of the show plus its high ratings are just two parts of the equation -- the third is literally worth its weight in gold to any network. Thrones has been nominated for Best Drama the last three years and taken home the prize in numerous other categories, ranging from acting to visual effects.

It's hard to break into the Emmy race during a show's first year but the series did it with style and hasn't looked back. Like those that came before it, Thrones has kept the network's tradition of award dominance alive and well, though thanks to AMC's (AMCX -4.41%) duo of Mad Men and Breaking Bad it has yet to win the top prize, which realistically could happen as early as next year (once Bad finishes its victory lap).

Yet many also recognize there will soon be a shot clock on the show -- the series is racing toward the end of its source material, which has prompted talk of the franchise moving to the big screen to wrap its run (once Martin concludes his opus). While Time Warner subsidiary Warner Brothers would conceivably be all for it, the move makes little sense financially for HBO itself, which wouldn't willingly bypass what would likely be continued ratings gains, a fact often lost in the conversation.

With tonight's episode Thrones will be fully through the first three books -- the third entry was split into two seasons due to its length. It is likely HBO will take the same approach with books four and five, meaning instead of two seasons, the network can get four out of the remaining novels.

If anything the pressure's on Martin as he has the hot hand at the moment. But just as there are numerous suitors for the crown in his books, so are there in the ratings race, and the winds of change are just as brutal in that world as any fictional one.