How do I love thee? Let me count the ways.
The Enchanted Castle An invisible princess, a magic ring, and more adventures than you could dream of. This is what Gerald, Kathleen and Jimmy find when they stumble upon a mysterious castle. At first it all appears to be a lark. But the children soon discover they need all their bravery and ingenuity to contend with the castle's supernatural forces.
The Railway Children When their father is sent away to prison, three London children move to the country where they keep busy preventing accidents on the nearby railway, making many new friends, and generally learning a good deal about themselves.
The Story of the Treasure Seekers When their father's business fails, the six Bastable children decide to restore the family fortunes. But although they think of many ingenious ways to do so, their well-meant efforts are either more fun than profitable, or lead to trouble — until one adventure has quite unexpected results. Sequels include The Would-Be-Goods and The New Treasure Seekers.
Five Children and It Before the children had had no idea that there was such a thing as a sand-fairy, now they were talking to "It". They discovered the odd-looking, cranky creature while digging. The fairy grants them a wish a day, lasting until sunset, but the wishes don't always work as they should. Sequels include The Phoenix and the Carpet and The Story of the Amulet.
This is an super-cool article about (among other things) Nesbit's influence on C.S. Lewis. Bet you didn't know she wrote a story called The Aunt and Amabel about a little girl who climbs into a spare room wardrobe and is transported to another world.