The Warrior Cats was well designed for a childrens series. It encorporated betrayal, love, anguish, detailed gore, and several other things. The cat's; if you could look past the occasionaly reminder of it's child-base were believeable.
TVtropes.org puts it quite well I think. I've read the books when I was young and they were one of my favorite series. I finished the final Omen-Book near the end of last year. The Ending was... strange and to me, arupt. But it was a good ending anyway.
"[In this book series, cats run wild in large family groups, fighting each other, falling in love, and worshiping their starry ancestors.
Those of you expecting sweet little stories about cats lazing about licking each other and falling in love are in for quite a shock (although that happens too, of course). The books are quite mature, thanks in part to Erin Hunter's Anyone Can Die policy, and the series can be quite graphic, as the characters face certain death and possible annihilation at least once a series, and, early on, usually once a book. They also grapple with questions of faith, loyalty, honor, and responsibility on a very regular basis. These books are about as child-friendly asWatership Down.
Yet kids are the target audience.]"