This is a review of the UK Hodder edition, credited to the fake author Lucy Daniels. In America, this would be published by Scholastic under the fake author name of Ben Baglio. The real author was Pat Posner, who also wrote Pony Parade and several other books in the Animal Ark Universe.
How do I know Posner wrote this? Just look at the copyright page or the dedication page. Whoever is given "special thanks" is the author.
At least it's easy to tell who the illustrator was. His name never changed despite which side of the Pond the book was published in. Paul Howard did all of the books in the Animal Ark Pets series. Often, he gives his animals cutesy human expressions, but he did a remarkably good job with the gerbil. He even paid attention to the text. This lost gerbil had a severely injured tail. Howard included this telling detail in his illustrations.
This was a typical Animal Ark Pets book in that it had other B plots to the main A plot of trying to find the Gerbil Genius a home. Other plots included the misadventures of a dog called Arnie, and studying harvest mice in the area. Also included were almost the entire cast of people we met so far in the series, and Welford regulars like Mrs. Ponsonby and her chubby dog Pandora.
Although there was some decent information about gerbils in here, one of the main factors in keeping a gerbil healthy is completely omitted. Gerbils soon die when they are forced to live alone, like the gerbil star of this book. They need to live in pairs, at least. This book covers a very short span of time, less than a month, but I can't think this gerbil would live too much longer unless he gets a buddy.