As far as Heinlein goes, this one is probably one of the least convoluted, and most child-appropriate.  That said, he falls into what I like to think of as his “short-book” pattern, where the first half is slow, plodding character development.  You get to know someone, get to like them…and then in the third act, we throw in crazy aliens and rescue him and send him back to Earth (hello, Have Space Suit — Will Travel). 

The premise is solid:  telepathic twins Tom and Pat Bartlett are separated to perform the ultimate science experiment.  While I greatly enjoyed getting to know Pat, the narrator, and Tom through Pat’s eyes, I felt the ending was rushed.  SO VERY RUSHED.  I get the happy ending that Heinlein always delivers, but it feels less satisfying because there’s not a lot of buildup or reason behind it.

Overall, I didn’t dislike the book, but it may not be the one I recommend.  It’s a good, fast read.  Just don’t expect it to change your life like Heinlein sometimes does.  If SIASL and TEFL are feasts, this one’s a snack.  Expect to be hungry again in a few hours.