
What is Un Lun Dun?It is London through the looking glass, an urban Wonderland of strange delights where all the lost and broken things of London end up... and some of its lost and broken people, too--including Brokkenbroll, boss of the broken umbrellas; Obaday Fing, a tailor whose head is an enormous pin-cushion, and an empty milk carton called Curdle. Un Lun Dun is a place where words are alive, a jungle lurks behind the door of an ordinary house, carnivorous giraffes stalk the streets, and a dark cloud dreams of burning the world. It is a city awaiting its hero, whose coming was prophesied long ago, set down for all time in the pages of a talking book.When twelve-year-old Zanna and her friend Deeba find a secret entrance leading out of London and into this strange city, it seems that the ancient prophecy is coming true at last. But then things begin to go shockingly wrong.From the Hardcover edition.
Kraken is the hunt for a giant squid after it vanished from a London museum.
Un Lun Dun is a young adult story of two friends who end up in a whimsical version of London.
I read the first few HP, and thought they were dreadful, and thus never read the later ones, so maybe I'm not the person you want advice from, but here are some recommendations of novels/novelists in the same genre (fantasy novels, written for children, that hold up for adults):
Nearly anything by Dianna Wynne Jones, but I particularly enjoyed The Lives of Christopher Chant, Archer's Goon, and of course Howl's Moving Castle.
Susan Cooper's famous Dark is Rising series. Half the series is more normal-kid (starting with Greenwitch), half is more special-magic-kid (starting with The Dark is Rising).
Garth Nix's Old Kingdom, starting with Sabriel.
While China Mieville is very much not a children's author (really! don't buy a random mieville book for your young niece/nephew, really don't!), Un-Lun-Dun is an amazing book in this genre.
China Mieville - Un Lun Dun
