I loved this book when I was a kid, so I was happy to find it stood up to adult reading. It's refreshing to find a tale of psychic children who use their powers not to save the world but to make their beds, harass their babysitters, and generally
act like kids. The conflict arises from misunderstandings between kids and adults, not some evil opposing force.
In short, there's no "with great power comes great responsibility" here, just good old-fashioned fun. And it is old-fashioned in a certain sense--the book is very definitively set in the late 1970s, with fashion and child-rearing attitudes reflecting the time period. But I think it would still be enjoyable for a modern elementary or middle school student.
My memory had the book running much longer, so I was surprised to see it ended where it did. Pity the author never wrote a sequel.