This is a review of the American Scholastic edition. It was originally published in the UK by Hodder. The real author was Susan Bently, who wrote some other books in the Animal Ark Universe. The illustrations were done by Anne Baum, who I liked much better than the original artist, Shelagh McNichols.
I've read seven of the nine Animal Ark Hauntings books, and this was far and away the best one. Because the other Hauntings books were so bad (though Colt in the Cave had some good moments), I shudder at the thought of reading the final two books. Not because they're scary, but that they're so poorly written ... not to mention going against the grain of the Animal Ark series. Or even going against the grain of Animal Ark Pets, which had started three years previously.
This was what a good ghost story should be ... just slightly altered from reality. Just enough to make you wonder. And not only that, it had good supporting characters, such as Bathsheba the cat, and two Yorkies and their humans.
My memory might be wrong, but I think we briefly see the book not told from Mandy's point of view. With the exception of short story collections, and I think Kittens in the Kitchen, the book that started it all, this is the only time we don't see the world through Mandy's eyes.