Those were my thoughts too. Since the two succeeding novels, written by his daughter Jane Leslie Conly, were published long after his death, we'll never know for sure what O'Brien himself would have made of them. Despite a couple of contradictions with the original story, I seem to remember the first sequel, Racso and the Rats of NIMH, being a pretty good read, but the second RT, Margaret and the Rats of NIMH, which involved the rats having to make communications with the human world, was somewhat weaker, and seemed to take things to an extreme even for an anthropomorphic fantasy. It was a pretty central plot point that the Rats of NIMH were able to read and write, but, unless I missed something, I don't remember it ever being established in O'Brien's novel that they could actually speak to humans in plain English.

"RAT" Update:
Tonight I came home to a surprise. The porch light was out so I couldn't see very well, but when I took out my flashlight I noticed something on the path leading up to the porch. My cat apparently left a present for me there.

It wasn't a rat, it was a mouse. A vary large dead mouse. My sister-in-law said it was the biggest she's ever seen. I'm betting that this is my "rat" as we don't have many rodents in the area and it's the biggest mouse I have ever seen. So I feel a bit silly for freaking out about this mouse. I'm glad it didn't die in the traps we set out... though death by a cat isn't so great. Oh well, Thank you everyone for your support and advice. It means a lot to me.