Disclosure: I have two tales in this anthology. My review applies to the other works.
Oftentimes, anthologies are uneven in quality. You'll have some stand-out gems and some clunkers ... and which ones those are depends a lot on personal taste. You won't find that problem here.
The premise of "Twelve Hours Later" is that each author's stories take place 12 hours apart. Ordered around the 24 hours in a day, the authors in this charity anthology spend time in Bath, Paris, Cairo, London ... and imaginary kingdoms. All of the work is alternate history, and some of it downright "steampunk." Standouts for me were the two Drake & McTrowell adventures (by David Drake and Katherine Morse), and the two Miranda Gray tales (by T.E. MacArthur).
All funds from sales of this anthology benefit local libraries. It's well worth investigating if you like this genre.