I have to admit I have no recollection of getting the The Green Ember, but according to Amazon I got it once when it was free. I'm the resemblance to Watership Down is what pulled me in.
The rabbits in The Green Ember are however, much more humanized than Watership down, fighting the wolves and birds-of-prey with swords and the like. Much of the story also takes place in a warren that acts mainly like a court and also feels that way. Into this world Heather and Picket, two young rabbits who have been driven from their solitary home, are plunged.
I liked it. It is aimed at somewhat younger readers, but this didn't bother me. As the story unravels there were a few twists that I didn't see coming, which was nice for a change. The writing was not the best, but I quite liked the story.