I was well into my twenties before I discovered E. Nesbit. Despite ravaging my local libraries as a youngster, it took me that long to come across her books. I have to say, it was worth the wait. She was a phenomenal young adult writer, despite the fact that she never intended to be. My introduction began with the trilogy which starts with "Five Children and It" and it was love at first read. She was imaginative, original and wrote for children without in any way talking down to them. After reading the 'Five children" trilogy, I spent the next few years tracking down other titles by her. I discovered "The Enchanted Castle", "The Wouldbegoods", "The Railway Children" and "The Magic World". I'm a sucker for magical adventure and these books never fail to deliver a sparkling, witty, unique environment in which to lose yourself. I highly recommend them to any parent searching for quality writing in this genre.
And if you already enjoy E. Nesbit, you should try Edward Eager. He supposedly patterned his writing style against that of Nesbit and did quite a good job. His books include "Half Magic, Magic By the Lake, Magic or Not, Seven Day Magic, The Well-Wishers, The Time Garden, and Knight's Castle.