This is one of the first books that my oldest son was excited about reading. He had been unwilling to move beyond Goosebumps and Animorphs. He had read an excerpt from a textbook and decided to give it a try. His motivation for reading it was the technology involved in the story.

Scientists at NIMH try to teach lab rats to read. They underestimate the rats' abilities, and the rats decide to gain their own freedom and create their own community.

The two sequels (Racso and the Rats of NIMH: 1986 and RT, Margaret, and the Rats of NIMH: 1990-both by Jane Leslie Conly, his daughter) are as good as the first book. They are worth reading again and again.
RL=4th-6th