There are so many TV shows that have been adapted from books and novels. Before you even think about getting deep into the seasons, you'll want to read the source material first. This isn't the case for all TV shows, but it is certainly the case for the ones on this list. The TV shows have just left far too much out from the books to really do the series some justice.

'Sleepy Hollow'

FOX has cancelled "Sleepy Hollow," but you may not have gotten into the series right away. You may be one of those waiting for the series to end to watch it all in one go. Before you do, make sure you ready about the real legend of the headless horseman and the story of Icabod Crane.

You will get a completely different story to the one on TV, but you understand some of the references made. In the TV series, Crane is awoken in the future. The novel by Washington Irving is set in the past, bringing history to life.

'The Handmaid's Tale'

This will be some of the most difficult reading you will ever do, but it's necessary reading. Hulu's current TV show "The Handmaid's Tale" is adapted from the novel of the same name. The novel, penned by Margaret Atwood, is actually from the 1980s but the current political climate has created the need to bring the story to TV screens now. While the series does an excellent job of telling some of the stories, there are clear additions and elements removed to create a more suitable-for-TV installment. The book series leaves a lot unknown, as it's told from Offred's view.

'13 Reasons Why'

It won't be that surprising if you've already watched "13 Reasons Why" on Netflix. However, if you haven't, you'll want to read Jay Asher's novel first.

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It's a beautifully but darkly written novel, telling the story of teenager Hannah who kills herself. But she doesn't just leave it all there. Hannah decides to let her classmates know why she did.

This has recently been adapted and seen through to the end. Hannah shared why she did it with a series of tap recordings. Now the teens have to live with the trauma experienced through the tapes, along with other trauma in their lives. "13 Reasons Why" season 2 is currently being written, but it won't be available on the streaming service until 2018. There is plenty of time to get through the novel.

Even if you've actually watched the shows, you need to read the books. They go into more details and tell the stories as originally intended. They may be uncomfortable to read, especially "The Handmaid's Tale," but they will be worth it to understand the shows deeper.