This Outlander novella tracks the story of Joan McKimmie (Jamie Fraser's stepdaughter by Laoghaire) when she leaves Scotland for France under the protection of Michael Murray (Ian Murray's elder brother who has a wine business in Paris) to become a nun. Those who read Gabaldon's novel Echo in the Bone will recall the two leaving on this journey.
The Space Between is a bit over a 100 pages and featured in the anthology "The Mad Scientist's Guide to World Domination" for those who wish to read it.
As is normal for Gabaldon these days (in my opinion), she writes far, far better when she gets away from Jamie and Claire. Joan is a fascinating character - we learn that she has more of the 'sight' than she's comfortable with, suffering with the ability to hear voices (shades of Joan of Arc) and see what can only be described as death auras -- shades that envelope people who are about to die soon. Joan's reasons for wanting to enter a convent aren't as pious as we perhaps thought in An Echo in the Bone.
For Michael's part, he is still mourning the death of his father, his young wife and their unborn child. When he and Joan accidentally tangle with another Outlander 'blast from the past' - the Comte St. Germain, things start to get very dangerous for both of them.
The Space Between is contains more information about time travel, for those who are interested in that aspect of the Outlander books, as well. All in all, it is a good novella - not astounding, but good - that brings back a couple of characters from earlier books for those of you with good memories. Personally, I enjoy Gabaldon's writing when she *isn't* writing about Jamie and Claire so this was a good read for me.