From Sherlock Holmes to Gossip Girl, television has always loved books as source material. But recently it seems like every new cable series is based on a hot novel or literary franchise.

Boardwalk Empire, Game of Thrones and The Walking Dead all have their roots in the written word. And most recently, Jonathan Franzen’s masterwork The Corrections has been rumoured to be in development for HBO, with director Noah Baumbach and Anthony Hopkins attached to the project.

Of course, there are deep historical connections between books and television: the popularity of episodic storytelling on TV builds on the tradition of the serialized novel.

But there are a bunch of reasons why books are more popular than ever in TV land.

Fans included

The main reason to adapt a book for television is the fan base – unpopular books rarely go televisual. But it’s not just about numbers.

Having pre-packaged fans means networks get demographic info before the show even airs: they know who will be likely to watch a show based on who’s reading the books.

This makes marketing the series a whole lot easier. You know young women will tune into Vampire Diaries and Gossip Girl. 

 Of course, the relationship is rarely one-to-one. The Walking Dead, among the most popular series on cable, has expanded far beyond its comic book audience, as has True Blood, whose ratings have risen dramatically since its first season.

Fragmentation and lowered expectations

With ratings expectations pretty low for both broadcast and cable – though rising for the latter – a book doesn’t need the sales numbers of Harry Potter to warrant a TV show (film studios often call dibs on those massively popular titles anyway).

Networks want guaranteed buzz and audience but they don’t need as many viewers as they once did to consider a show a success. Cable nets like HBO, meanwhile, care almost as much about innovation and prestige as ratings , which explains their interest in The Corrections.

So much drama

Book-to-TV conversions work better for serious content, and despite the much-touted “return of the sitcom,” dramas are still pretty popular, especially on cable.

For the dozens of channels trying to establish their brands in a competitive marketplace, dramas can bring both ratings and critical acclaim. AMC, the once-fledgling cable network behind Breaking Bad and Mad Men, is a great example.

If you’re new to original programming, developing series from pre-existing properties is a good way to ensure some level quality. Netflix recently did this with House of Cards (a British TV series and novel) and so did BET with 8 Days a Week (adapted from The Come Up book series).

Books bring quality

While some may wonder whether the years of “quality TV” are coming to an end – especially with the flood of horrible sitcoms this fall – most networks rely on quality programming, and books are an efficient way to get it.

For decades, Americans perceived British television as better and more serious, and many of those “masterpiece” programs came from Brits mining their literary canon of Austen, Brontë, Christie, Doyle, Eliot, and company.

The notion that books equal quality TV is, if not always true, an enduring assumption. Dexter isn’t Miss Marple, but the basic idea still stands.

Unarrested development

Just as studios fear lackluster box office debuts, networks fear expensive shows that premiere weakly. Brand name titles didn’t help Pan Am (still alive) and The Playboy Club (canceled) this season.

Book adaptations save producers the trouble of convincing executives a series has enough clout to generate headline-grabbing premiere numbers. Network executives, meanwhile, can sell the idea quicker to higher-ups.

It’s the same reason why U.S. television networks have a newfound love for British television series – Prime Suspect, Skins, Misfits, Inbetweeners – and American movies – Teen Wolf, Friday Night Lights, et al.

Are TV series based on books any better? Certainly many of my favourite dramas on-air right now were previously in print. But books also bring challenges, including how to translate beloved print characters to the screen, and how to condense complex stories into manageable lengths.

Unlike books, television series cost millions and can be canceled ruthlessly. Game of Thrones could end up with many more seasons than there are books, but if ratings go down, TV fans will be left without a satisfying conclusion. Who has time to read those novels?