Outlander has been a big hit for Starz ever since its premiere back in 2014. Based on the ongoing book saga by Diana Gabaldon, the show has understandably been compared to HBO's smash hit Game of Thrones, which itself is based on a book saga by George R. R. Martin. That said, the stories have mostly been told in different ways. Game of Thrones departed from the plot of the novels in some key ways quite early on, and later seasons combined events from different books and even outpaced the book material currently available. Outlander on the other hand has been largely faithful to the books, with many of the changes happening due to the limitations of the television medium as compared to the saga as written.
According to Outlander executive producer Toni Graphia, however, Outlander's handling of the book material may change in the coming seasons. She had this to say:
Future seasons of Outlander may take liberties with adapting the source material in the order it was written, which is Game of Thrones fans who have also read the A Song of Ice and Fire books know well. Season 4 will be based on the fourth book in the Outlander series, called Drums of Autumn. Perhaps readers will notice elements from the fifth, sixth, seventh, or even eighth books included in the plot. Granted, future books tells very different stories than what happens in Drums of Autumn, and each book takes Jamie and Claire in some very different directions, so there are undoubtedly limits to how much seasons of Outlander can borrow from future books. Still, we may no longer be able to count on seasons corresponding with the books as numbered, and that's very Game of Thrones.
Given that Game of Thrones is one of the biggest hits in television history, the Outlander team could do worse than begin working with a similar framework of only loosely adapting the novels to the corresponding seasons. Then again, Game of Thrones had no choice but to go in its own directions at a certain point when the showrunners ran out of books to use as source material since George R.R. Martin has yet to publish the last two installments of his seven-novel saga, and the show will end before the sixth book even hits bookshelves.
Diana Gabaldon has already published eight installments in the Outlander saga (which will probably run for ten), and she tends to publish one every four or five years. Since the eighth book became available in 2014, we probably won't have years and years to wait for the ninth. Basically, Outlander -- which is only heading into its fourth season -- won't outpace the books any time soon. The Outlander showrunners almost definitely won't run out of material to adapt.
Outlander does seem fairly determined to keep the show in line with the book series. Diana Gabaldon revealed at an Outlander panel (via EW) how closely she works with the folks at the show:
At the very least, book readers seem to be able to count on the show not spoiling huge twists that will take place later in the books, which almost certainly can't be said for A Song of Ice and Fire readers who watch Game of Thrones. Diana Gabaldon's involvement with the scripts and episodes indicates that the show will stay at least consistent with a lot of the material in the books, even if seasons are not exact adaptations from the corresponding books.
Unfortunately, we have a while to wait until we get to see more Outlander. The fourth season won't premiere until the fall. For what has been revealed about the next batch of Outlander episodes, take a look at our breakdown of what we know so far about Season 4. For what you can watch while we wait, check out our midseason TV guide and summer TV schedule.