Once upon a time, a man named Douglas Adams wrote a brilliant novel called Dirk Gently's Holistic Detective Agency. A few years later a British television series arrived that was inspired by this book and really rather good, even if it wasn't a direct adaptation of the book. It was promptly canceled after only a few episodes. Then a few years later BBC America took a stab at the license and created a new show based on the book. In typical American fashion they opted for over the top nonsense like secret CIA projects and slapstick humor to appeal to audiences. Unfortunately, this worked and the show continued for two miserable season before it was canceled. This makes Dirk Gently's Holistic Detective Agency the only book I know of that spawned both a great television show of the same name and a completely horrible one. I suggest you don't confuse the two.

There are too many fantasy and science fiction shows based on books, so they all end up looking the same after a while. For really good shows watch Outlander, which is based on the book by Diana Gabaldon and House of Cards, which is based on the book by Michael Dobbs. Not many people know this, but Poldark is also based on books by an author named Winston Graham.

I've been burned too many times to consider any television shows as equal to the books on which they are based. Just look at flops like Lipstick Jungle or how badly they butchered The Southern Vampire Mysteries series of books when it got turned into True Blood for television. My advice is to avoid disappointment and just stick to the books. Even the "best" shows based on books have to make compromises and just end up as pale imitations at best or complete abominations at worst.

With the amount of books that have been turned into television shows late, I strongly suspect that most authors are writing their books in the hopes of landing a Netflix deal. Having said that, there are some shows that actually manage to be at least as entertaining as the books. Sherlock (the one with Benedict Cumberbatch and martin Freeman) did a good job mimicking the suspense of Arthur Conan Doyle's books, while American Gods pushed new boundaries on television by using the Neil Gaiman novel as a basis.

This is the type of question where the answer would depend on what exactly you are expecting. If you are just looking for good television shows based on books there are plenty to choose from. If you are a fan of the books and want a television show that accurately follow the events portrayed in the books, then things get a little more complicated. Few shows are able to capture all the intrigue and nuances of the books that they use as source material, which inevitable upsets some fans. Even the mighty Game of Thrones, which is considered by most people to be the best television show based on books, had to leave out a lot of stuff. Shows based on books have definitely been getting better as television budgets increased, but even the best will still fall short compared to the books in my opinion.

Game of Thrones. If there is one show that exceeded all expectations and set a new benchmark for television shows, whether based on a book or not, then it is GOT. The only other shows that come close are The Handmaid's Tale and Orange is the New Black.

Well, they are called comic "books" so I guess that means that they count, although none of my teachers in school ever thought so. What I don't agree with is that The Walking Dead and iZombie being "good" shows based on books. It is true that both of them have started out very strong and stayed true to their source material, but I have found that both shows began to drift after a couple of seasons. iZombie in particular had a terrible (what i thought was) final season that felt to me like it tried to change the personalities of all the major characters. I haven’t started watching the new season yet so I don’t know if this changed. The Walking Dead also went from being an emotional roller coaster, to a show that just seem to revel in the violence for the sake of shocking people. As for the Marvel comic book movies, they are all just cash-ins. I think that the market is over saturated when it comes to superhero stuff and it is really starting to show. Just look how both Luke Cage and Iron Fist were canceled.

Do comic books count as books? Because if they do, then you can definitely add The Walking Dead and iZombie to the list of good shows based on books. Of course, almost everything based on the Marvel comics are also very decent, so keep an eye out for Jessica Jones, Luke Cage, Daredevil, The Defenders, The Punisher and the rest. None of them are perfect, but they stay true to the spirit of the books.