I've been waiting for this for a long time. I am one of the lucky few who bought _Sorcery and Cecelia_ when it came out the first time, and I still have my battered old paperback of the first edition -- as well as newer copies of the reprint, and the first sequel _The Grand Tour_.
For those who are unaquainted with the series, it is an epistolatory novel, set in a world with magic. [The first one was set in the Regency, but it has been ten years since the first two books, so now the former Regent is King.]
In any case, _The Mislaid Magician_ was absolutely delightful. It is like visiting old friends and catching up with them and their lives.
Just the thing to cheer me up.