Many popular television series are adapted from books, but fans of The 100 have long since discovered that reading Kass Morgan's book series has done little to reveal show spoilers. The show and the books are so different, in fact, that they only share the same general premise and a handful of characters.

With that said, let's explore why The CW's version of Morgan's The 100 has little in common with the book series it was adapted from.

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When The 100 was optioned for a series at The CW, a lot of changes were made to the source material. While Morgan has discussed that she was happy with the alterations, the reason the adaptation strayed so far from the source material is that the network jumped at the chance to make the story into a live-action show in 2013, well before the entirety of the book series was released.

The CW series premiered on March 19, 2014, only a few months after the first book was published in September of 2013. Therefore, the show was in production far before the release of the first novel, meaning that the creative team, including showrunner Jason Rothenberg, had little to go on besides the premise and what was offered in the first book. And, since the next three books weren't released until after the series had already begun airing, it was unable to be more than a loose adaptation of the source material.

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Fans of HBO's Game of Thrones might recall while the first few seasons of the show were close adaptations of the books, once the creative team ran out of source material to adapt, they were forced to improvise and divert the story. This occurred for almost the entirety of The 100, with there being little source material available when the series first started developing its story.

This disconnect obviously led to massive changes, including some to the series' main character, Clarke Griffin, who is one of the four POV voices in the book. In the source material, she is arrested and convicted of treason early on, while in the show, she is locked up innocently. Clarke's mother also plays a much larger role on the show, and she is also a far more ruthless and authoritative character.

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Some of the other noticeable changes between the books and show occur because characters were either added to or omitted from the series. To amend for this, the powers that be opted for some characters to swap traits or become combined with other characters. Finn, Murphy, Jasper, Raven, Charlotte and Monty are all examples of characters featured on the show that didn't appear in the books in the same capacity. Additionally, there are also characters featured in the book who don’t make it to the adaptation, including Glass.

Moving away from character differences, one major thing that changed in the adaptation is the general tone. While both series are foreboding, the show is considerably darker due to the stakes. This also reflects the decision of the creative team to focus far more on war and moral consequences of action, injecting a tone of never-ending dread into the world it builds. One reason the stakes are upped on the show is that the characters navigate through different worlds, while the books largely explore Earth. The show also focuses far more on expanded world-building, revealing far more moral depth than the books it was loosely adapted from.

The 100 stars Eliza Taylor, Marie Avgeropoulos, Bob Morley, Lindsey Morgan, Richard Harmon, Tasya Teles, Shannon Kook and J.R. Bourne. The series airs on Wednesdays at 8 p.m. ET/PT on The CW.

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