Basil the Great Mouse Detective is a book based on a Walt Disney film that was based on a book by Eve Titus and Paul Galdon that is itself a pastiche of Sir Arthur Conan Doyle's Sherlock Holmes Stories.

The idea is that the mouse Basil - named incidentally in honour of Basil Rathbone, the actor who famously played Sherlock Holmes in a series of fourteen films during the late 1930's to mid 1940's (see the joke here rat-bone), lives in the same house as his human counterpart and leads a parallel life as The Great Mouse Detective.
The Disney film itself was highly praised, and if you have seen it then this book follows that story line; but as a stand alone tale (oh dear! I've made another pun - tale/tail) it failed to engage my six year old that much. I think it is because the main characters are far too self absorbed and detached. The book opens with Dawson, nose-deep in a newspaper while trying to get Basil's attention, who is himself ignoring everything else around him and concentrating on either transferring fluids from one test beaker to another or peering down the lens of a microscope. In the film this may have served to build atmosphere? But in this adaptation it just does not work. Even when the little girl mouse arrives on the scene, Basil is dismissive saying "I just do not have time to chat with children.".
Only when the peg legged bat Fidget appeared did my own youngster start to take interest. Mainly because she played up to this element of fear, which intensified with the discovery of the arch-villain Ratigan.
Although the anamorphic animals live in the same time-line as the humans and are at the same technological level and dress in the same fashions; it appears that although England was by this time governed by Parliament, the rodents are still living under a monarchy with absolute rule over them. This is how Ratigan aims to gain power, by replacing the Queen with a puppet - literally!
Having already kidnapped the young girl's father who is a scientist, and being coerced into building a functioning robotic Queen under the control of Ratigan; he also temporarily imprisons the young girl - until The heroes arrive on the scene.
The plot is that once the robotic impostor has named Ratigan her successor, he pans to rule the kingdom and demand all the wealth to satisfy his own greed. Of course Basil is not about to let that happen.

I would suggest that you track down the original children's book as some of these Wonderful World of Reading versions can feel a little rushed and pointless. This I would say is probably the case with this one, unless your child has already seen the movie at which point their own imagination may be able to fill in some of the gaps left in the storyline as well as the lack in personality projected by the protagonists in the story.

I happen to be a big Sherlock Holmes fan myself, and so I found all the little references in the story amusing on an adult level; and I must now track down this film as I am sure it is will make good family viewing. Perhaps then, we may revisit this book.

Conclusion: Film tie-in value only. ( )