Netflix's latest series, Firefly Lane, doesn't just mark Katherine Heigl's return to TV — it's also the first time one of bestselling author Kristin Hannah's books has been adapted for television. As a result, Hannah's fans surely have high expectations for the decades-spanning tale of Tully Hart and Kate Mularkey's friendship. But book fans should brace themselves, because while the general arc of Tully and Kate's story remains intact, Firefly Lane takes some interesting detours from the book along the way. (Warning: Spoilers for the first season of Firefly Lane follow.)

Some of the swaps are small — Kate's little brother from the book becomes her closeted big brother on the show — but others are more dramatic, including a serious departure from the book's tearjerker ending. Let's just say that the door is left wide open for more seasons as a result of that last one, which is good news for anyone who wants to see more of Tully and Kate in the future.

From the addition of new characters to the exclusion of others (sorry, Kate's twins, you just weren't dramatic enough for this world), I've chronicled every major change Firefly Lane makes from the 500 plus page book it's based on.

Johnny & Kate Are In The Midst Of A Divorce

Book fans, you might want to sit down if you're reading this before you watch the show: Johnny and Kate are in the process of getting a divorce when the series begins. I know, it's too tragic to contemplate, but their split does make for good drama.