... the dialogue was very repetitive.
This is an issue he has in all of the DF books as well. He will use the same word three times in two sentences, for example. Or, he will say something in one sentence and then repeat it with different wording in the next. It feels like these are instances of him just pushing through lack of inspiration to keep on deadline with the intent to fix it later. I think he would benefit a lot with a stricter editor who is more willing to make red circles around these for the re-write because they just go through now to the detriment of the work. If I am remembering correctly, he even once described a lion's roar as leonine.
And, Dina, I am glad you liked the characters. I think I enjoyed the cat character the most because he seemed to be intentionally designed as two dimensional. I didn't expect any depth from him and wasn't disappointed. He was fun and funny.
The DF characters started out two dimensional as well, I think, but have expanded over the course of the series. The writing is also awful for the first few books and that doesn't help. I think the first person perspective helped hide a lot of the shortcomings, though, because we only know what Harry knows or chooses to share about others but we still get a sense of intimacy because were are inside his head and exposed to all his feelings.