Fables: 1001 Nights of Snowfall is a prequel volume to the series, published after volume 7, Arabian Nights (and Days). An original hardcover, it contains ten stories of widely varying length, mostly about characters already met in the series. (The two exceptions are also the shortest, just three and two pages, and thus are unsatisfactory on two different levels.)
On the whole, I thought this was a solid prequel. My favorite backstories were of the Frog Prince and Frau Totenkinder, which illuminated new aspects of the characters. I felt the other stories were less revealing and thus less interesting, though I’ve no objection to reading about Snow White, Bigby, Reynard, and King Cole.
In the usual way of prequels, I think it’s more interesting if you already know the characters, though it may be easier to find in libraries and thus convenient even if you haven’t read the series.