I just finished it the other day it was the best ones out of the whole series (i thought) but it is definitely my favorite book from the warriors series now!
Well it takes place between the darkest hour and midnight, and it Tell's the story of when firestar travels far away from his clan soon after the battle with bloodclan to rebuild the fifth clan "skyclan". Fifth clan?! Yup that's right there used to be five, but you'll find more out about that if you read it. But it's a really good book. firestar and sandstorm have to rebuild and entire clan from scratch because it was lost 2 generations ago. the only reason firestar is doing it though is because the former leader of skyclan kept visiting firestar in his dreams and told firestar that it was his destiny to rebuild the fifth clan.