I first discovered Diana Wynne Jones when I was twelve and shelving books in our middle school library. There I found Witch Week which I love. Since then I’ve read and reread all of the Chrestomanci books, and several of her other books, and always loved them. She’s a fantastic author.
The Pinhoe egg is very good. It explores more of Chrestomanci and Cat’s worlds, it has griffins and magical creatures… but honestly? After the others, it is a bit of a let down. The action takes a long while to build up, and then climaxes quickly with no real “the characters figure things out for themselves” per say. No real danger in a typical way for her books. So, whilst I liked it, I don’t find it comparable to her other books.