This book starts as the last one ended, with part of the pack heading to the human world. It would definitely help if you have read the first book, as a lot of the character and world-building was done there, and I think people who haven't read it would be quite confused.
As with the first this book doesn't have an ending. Some of the story has progressed, new twists have appeared, but there isn't a definitive ending, since there is another book to come. I like having a satisfying ending in my books, even if there is more of the story to come, so if I read them again, I would read them as one book, back to back.
That being said, the story is well written, the characters develop even more, and the world expands, making it an enjoyable read.