If I'd read this book in the early 1970's, when I was a young teenager, I would have loved it. Cryogenics mixed with time travel... a feast for a young science fiction fan. Unfortunately, reading it for the first time in 2012, it seemed much too cozy to be written for a contemporary adult. Except for the boring details of patents and company stock. Those I found tedious and unnecessary, not cozy at all. The fact that the novel was written in the 1950's then staged in 1970 and 2001 would have stopped me from buying it had I known. I expected the far off future, since, apparently, the novel is still very popular. It was difficult for me to accept a futuristic premise when the fictional future is in my actual past, and it is not recognizable. Heinlein likely never imagined that people would still be reading his book more than a half century later. Then there's the fact that the actual time travel happened way too late in the novel for me, past halfway. The details of "cold sleep" (cryogenics) and robotic engineering weren't interesting enough to engage me for more than half the book. I found the plot surrounding the main character's double-crossing partner and girlfriend to be foolish melodrama. However, the last quarter of the book redeemed the novel somewhat. I enjoyed that part enough to raise the rating from a 2 to a 3. The problems posed by time travel were discussed too briefly but interestingly.