What's missing from Nesbit that I think Lewis accomplishes is character development. Everyone who has read Narnia knows that each of the children have distinct personalities. Nesbit's siblings are somewhat interchangeable. I couldn't always tell them apart.
Two characters in the book with well developed personalities, however, where the Psammead - crotchety, vain, easily offended, tricky; and really, Martha the maid, although in reality perhaps Martha was a representation of "Every maid"; certainly she was as distinct as the Psammead.
A century and some change later, the book holds up remarkably well. It's still later Victorian in setting, but the fantasy elements overshadow some of the more confusing bits related to the era (clothing, slang, servants, etc.). Although Nesbit set this in the "real world" in 1902, things have changed enough since then that it could feel like a fantasy land. The brothers and sisters could still fit neatly into a Lewis novel (friends of Digory and Polly); they could also be characters in a Diana Wynne Jones book. They are the ancestors of Harry Potter and his gang, although Harry and company have evolved into something completely different from the five children.
The best chapters are the first ones - "As Beautiful As the Day" and "Being Wanted" are really hilarious. The "Wings" chapters were also quite good.
My rating: 4 of 5 stars
Five Children and It is the ancestor of the Narnia books, and even Harry Potter (with a dash of much else). And although children's fantasy has evolved much since 1902, Nesbit's book is still charming, witty, and enjoyable. The narrative point of view is what makes the book special (and is a direct line to C.S. Lewis and Narnia) with the omniscient, wise, witty, slightly sarcastic voice that finds adults silly and stupid; sort of like being told a story by a much loved uncle or aunt who is only slightly older than you, a bit wiser, but still understands what it's like to be a kid. The stories at the beginning are best; "As Beautiful as the Day" and "Being Wanted" are fantastic and funny. The five children are almost interchangeable - it's the crotchety, vain, overly sensitive Psammead who steals the show. This century-and-some-change years old story will still have appeal to modern children; the clothing, slang - and servants - are merely window dressing to a great story.