I read them when they came out and have always thought Phillip Pullman was a far better writer. A more fearless writer, but also a different one.
HOWEVER, I've read the first three to the daughter in the last 3 months and I have approached them from a very different mindset.
The first one is obviously a first book, it may not be amazingly well written, but it's inventive, exciting, the story whips along, it's engaging, and from the viewpoint of now, it actually really rather lovely seeing a novice writer at the very beginning of what becomes a massive phenomenon.
The second and third, you can see her begin to hit her stride. The stories are still very exciting and her writing develops. It really interesting watching her develop as a writer.
And they do get really quite dark - deaths come in book 4 onwards.
Also, she has clearly thought so much about it - it's a fully formed world and a very exciting one.
But, 6 and 7 could have done with some editing, a lot of editing.
I'd say read them, with an adult's approach, and understand the jokes, the wordplay, the cleverness. And enjoy them.
There's nothing to be sniffy about in an adult reading kids' or YA fiction, a book is a book is a book. I don't give a damn if you're reading Proust in the original French or Enid Blyton in an expurgated version. Start, and if you like them then press on. If you don't, no great shakes!