It probably goes without saying that this book is essential reading for fans of Diana Gabaldon's Outlander series and related works. I really have no idea whether the stories contained in A Trail of Fire would be at all interesting for newcomers to her work -- certainly, there's some well-researched and written historical fiction here, but I have a hard time seeing it being meaningful to anyone who hasn't read her other books and isn't familiar with the characters. 
 That said, what a delight it is to have the four novellas contained in A Trail of Fire all in one volume! Three stories have appeared previously in other anthologies, but the new one, The Space Between, won't be published in the US until spring of 2013. 
 It's plain and simple: If you love the Outlander world, read these stories. 
 Updated to add: A more detailed review is now posted on my blog.