In "The Short Second Life of Bree Tanner" we know now from the perspective of these Geschcihte newborn - just Bree Tanner. They appeared in Eclipse on short and now we learn about Victoria, the Volturi and how the Cullens's unusual act in such a newborn.
The Novella is quite short with 178 pages. And that's a shame, because the romance between Bree and Diego by simply not acting authentically. I know vampires experience love in their own violent nature, but I take the strong attachment to Bree Diego simply not starting. There is something more bonding scenes would have been necessary. Otherwise, I think the story exciting because it just shows a very different vampire life. The best part for me though in fact the final, when Bree meets the Cullen's. This is perhaps the fact that you already know the scene and it is understandable for the reader. The information can come Bree Edward through her mind are priceless for the Cullens and raises again a new light on the progress of the Twilight story.
Conclusion: For Twilight fans a must! Solid parallel story from the Twilight universe.