This is another one I wish I could give 3 1/2 stars. It's stronger in the first half than the second half. But I usually read fiction, so this is a bit out of my comfort zone anyway. And Sobel does a good job of allowing for that - bridging the gap between intellectual types and people (like me) who left the academic tomes behind when they finished college.
One thing Sobel does really well - other than convey the titular material - is establish how different things were 'then' than they are now. There are some interesting side-stories, which she touches on briefly. She also keeps things moving at a decent pace, as though she's aware she can't take her readers' attention for granted. However, there is some jumping around chronologically which is mildly confusing. The descriptions of clock innards are also a bit confusing, though necessary probably. A time-line of the key events would have been a good idea.