The warm reception of Paradox in Oz led to Einhorn penning another Oz book, The Living House of Oz, which was published in 2005. If you read up about Unauthorized Magic, you can guess that the titular house is the same that Buddy and his mother live in.
The story opens by elaborating on the little we learned from Unauthorized Magic about the House and its inhabitants. Buddy and his mother are very devoted to each other, though she often spends most her time working on her unlawful enchantments.
Also, some of the formerly inanimate objects are introduced. Most have personalities based on what they actually are, but the most eccentric character among them is the Earl of Habadashery, a living hat stand. When a question arises among the inhabitants of the Living House, the Earl immediately fabricates a ridiculous answer. Don't worry, though, this is not so overdone that it gets irritating. In fact, the Earl becomes endearing and actually manages to save the day at the end. (Just how you'll have to discover for yourself.)
The Living House has recently relocated outside of Tonsoria, a kingdom Einhorn mentioned in Paradox in Oz, but we only met its young girl ruler then. Coming across Brussle's Barber Shop (which Ozma visited in Paradox in Oz), Buddy finds it deserted. Princess Ayala of Tonsoria arrives and meets him, but then both are kidnapped by men in large wigs!
Looking for her son, Buddy's mother arrives in Tonsoria, consulting Sir Dye, Lady Twist, and Princess Talia, Ayala's little sister who knows more than anyone could guess. When Buddy's mother uses magic to show where Ayala and Buddy are, Glinda arrives on the scene. Upon questioning, Buddy's mother reveals her name is Mordra, and everyone sees she looks like a younger version of the Wicked Witch of the West!
For the time being, Glinda allows Mordra to help her find Buddy and Ayala, but when a mysterious beast arrives, Mordra panics and transports herself and Buddy back to the Living House. However, Glinda soon arrives and arrests Mordra and takes her to the Emerald City.
As for Buddy, the Earl, and the rest in the Living House, they can only do what they feel is right: go rescue Mordra!
On the journey, Buddy meets many interesting characters, some from Baum's books, some of Einhorn's creation. And soon, Buddy becomes an item of speculation himself, he appears to have some sort of magical powers of his own. Where did these come from, however?
And as for Mordra, what will Ozma do to ensure that her law against unauthorized magic will not be broken again? (By the way, a very humorous trial occurs in that storyline.)
The Living House of Oz is filled with humor and adventure, very different from Paradox in Oz, but we weren't asking for that book again. While I loved the brain-bending puzzles in Paradox, Living House is written in a way that you don't miss them, as they aren't really important to this plot. Einhorn proved he wasn't going to write the same story twice, and that's the most you should ask for from any author.