Erin Hunter's cat based Warriors series gets an entire shelf to itself in my library, so obviously I grabbed one as part of my Reading My Library quest. As I have since learned, the books are grouped into various series, and then numbered within those series. I brought home Sign of the Moon, Book 4 of Omen of the Stars, which my son informs me is, like, the third series. His literary soul shudders at the idea of entering a series in the middle; he'd rather show up halfway through a funeral and tromp on down to the front row.
The book seems a happy enough middle grade book, with diverse characters whose names I can't remember but which I never got mixed up. There was a lot of references to prophecies that I don't know about and conflicts that I didn't fully appreciate and many of the characters clearly had a Past, but the current events were marked clearly and I like the feeling of backstory between characters that looms larger than my knowledge.
I'd put these books in the same library as Ranger's Apprentice -- good clean fun that doesn't leave much aftertaste. I didn't feel that I had a broader understanding of the human (or feline) soul after finishing it, but it was a pleasant way to spend an afternoon, and the idea that these are cats wrestling with clan boundaries and ancient propecies and mystical sleep journeys gave extra spice to the time. I won't chase down all these books for myself, but I'd be delighted to see elementary age kids chewing their way through a few dozen of them.