I read The Sword in the Stone, by TH White, fairly quickly, and I found it pretty fun. It’s endearing and amusing, and I can definitely see why it appeals to children so much. It’s basically a collection of small adventures, involving time spent as a variety of animals, jousting, magic, meetings with Robin Hood (pardon me; I mean Robin Wood), and more.
Overall, though, there isn’t much central purpose to the book. The “plot” (from which the title is drawn) only really shows up for the last 10 or 20 pages, and it isn’t outlined in much detail. It all just happens basically as a summary, and then it’s over. I would have liked to spend another 50 pages reading about the details of the sword in the stone, and how it affects Arthur, and Merlyn’s departure, and so on.
But kids probably don’t care about that aspect of things all that much.
Overall, it’s a fun read, and not too long, so I’d recommend giving it a look.