Great read, with some violence and references to Evolution.
Mrs. Frisby is a widowed mouse who just wants to do what is best for her family. But when her son Timothy gets sick, she has to go to the rats of NIMH for help. Subsequently she learns some of their secrets and what they have to do with her dead husband - and herself.
Pretty high. The rats have lived all of their lives by stealing and feel guilty about it, and work to find a way to support themselves.
None, except there is a regrettable acceptance of evolution: once in a piece of dialogue that suggests that the evolution process could have stopped at rats if they weren't lazy; and also in the implication that evolutionary science was used to create a new species of rats.
There are several references to the dangers of a mouse or rat from the farm cat, Dragon, who has killed a specific mouse in the past.
In NIMH, the rats (and mice) go though animal testing, receiving regular injections and electric shock.
Drug and Alcohol Content
There are uses of sleeping powders (on a cat) and medicines.
Crude or Profane Language or Content
"Mrs. Frisby and the Rats of NIHM" was a delightful read from start to finish, with engaging characters and a great plot; it sucks the reader into the lives of the Frisby family and that of the rats. It would make a great family read, where the evolutionary content could either be skipped or explained to young children.