Ok, the first 6 books were decent, but from there it goes downwards. The New Prophecy books arent really entertaining and the Power Of The Three has an odd, stupid final plot twist. In The Omen Of The Stars everything is ok. Even if Pigeonflight is the main character, she has 0 personality. The next books are fine, but everything gets so bad in the A Vison of Shadow.
There are too many characters and this way most of them have little to no personality. The writing style is poor and the feelings, dialogues and thoughts of the cats are not realistic. After the first books became relatively popular, I have the feeling that Erin Hunter (or the team of authors who wrote the books) continued writing just for money.
But the most important part is that this books are literally Watership Down with cats, not rabbits. Erin copied pretty much the idea of the Watership Down book. But then added so many clichés I could puke.
But Jayfeather has a cool personality and Yellowfang too.