You don't know me, but I have been a fan of your books since I was around ten or eleven. I understand you're well-known for your quirky books like My Teacher is an Alien, but I'll admit I've only ever read your fantasy work, such as the Magic Shop series. I loved loved loved Jeremy Thatcher, Dragon Hatcher. But the work that has influenced me the most has been The Unicorn Chronicles.
There were only two books, Into the Land of Unicorns and Song of the Wanderer, when I first discovered Chronicles. I searched in vain for more, since it was obvious the story was meant to continue. I asked librarians. I used my abysmal internet skillz to see if you had died or had given up or if I was just stupid and the library lacking. But to no avail.
Years went by. Then, one day a year or two ago, I happened across the third volume in the series. Eagerly, I snapped it up and read it in scant hours.
Years more went by until yesterday, when I was deliberately combing the shelves and found the fourth volume. I snapped that up too and stayed up until one in the morning finishing it. I was exhausted today in my early-morning class, but having finished a beloved series from my childhood was well worth the hours of lost sleep.
In the letter before the fourth volume, you mention that you started the series in 1991, the same year I was born. I discovered the books at about ten or eleven, meaning that the books I read were at least several years old. Having looked it up, the first was published in '94, the second in '01, third '08 and fourth just this year in '10. This series has taken my entire lifetime to be published.
I am one of the readers you mention in your letter who started reading the series in childhood, have since grown up, and yet were still wanting you to finish the series. I noticed too that your books seemed to grow up too. The series went from a simple escapist story of a girl going into the land of unicorns that was perfect for my younger self, to an epic with its own take on myth and legend, dealing with mature themes like death and love and family, that was a very satisfying read for my present self. I was able to enjoy the work as much for itself as for its nostalgic value. And for that, I thank you, even if it took you nineteen flippin' years to get the darn thing out.