Books based on roleplaying games, in my experience, are hit or miss with only the most razor-thin middle ground. Some take such extraordinary liberties with the source material that the only thing the book has in common with the original setting is the game's logo on the cover. I'm pleased to report that In Northern Twilight is quite a hit.
Jess Hartley accomplishes the miraculous feat of telling a compelling story that is designed to give insight into two of White Wolf's Exalted game line's most iconic characters, Swan and Arianna. She tells their story in her own way and at her own pace, while remaining true to what we already know of the characters and the setting. In the end, what we get is not a regurgitation of facts from game books but rather a fun adventure that builds on previously existing material and adds depth to otherwise stereotypical characters.
If you're looking to introduce someone to the world of Exalted through novels, I'd recommend bypassing the previous books in the Exalted series and handing them this one. And, of course, if you're a fan of either Swan or Arianna, or both, this is a must read!