Here are my brief comments, book by book:
Magic Steps, book one -- No complaints here. The story didn't draw me in as much as some of Pierce's other books, but that's ok.
Street Magic, book two -- Good story, lots of character development and it raises questions that make you think. I was distracted from the story though because I found several grammatical errors throughout the book. I'm not talking about grammatical errors in the character's dialog (Pierce likes to have her characters speak in different accents and dialects), but in the description of scenes and things like that.
Cold Fire, book three -- Again, good story. No grammatical mistakes. It's funny, when I sit down to write this post I was going to complain about a side plot never being resolved in this book, but I just remembered that there was a resolution to it. So never mind.
My guess is that there were multiple deadlines when Pierce was writing Street Magic (after all, she also released Protector of the Small: Squire that year) and that she didn't get to spend as much time editing Street Magic as she would have liked. Based on my memory, Squire didn't suffer at all from being just one of two books released in 2001. And just to be fair, I want to note that two books were also released in 2002 (Cold Fire and Protector of the Small: Lady Knight) and both of them were well edited.
These are fun books, and maybe I'm just getting nit picky about grammatical errors in one book because I'm an English major. They're fairly minor and I could count them on just one hand. That's more than I could say of some authors.
I plan to pick up the final book in this quartet tomorrow, and I look forward to reading it. :)
What are you reading this summer?