I can't really summarize Timepiece for you without spoilers, but I'll try. Told entirely from Kaleb's point of view, Timepiece is an all out hunt for Jack Landers, one that will have dire consequences should Kaleb, Em, Michael, and Lily fail to find him. The rips are becoming more and more common place, huge scenes instead of just a person or two and things definitely aren't looking good. But why is everyone after Jack? That, is something that you'll find out should you read Timepiece. 
 In the spirit of being completely honest, I will say that I couldn't completely get behind seeing things through Kaleb's eyes. I love how it allows the reader a more in depth look at him; but at the same time, I usually have a hard time getting behind male first person point of view narratives. That's not to say that I disliked it or that it took away from the story--it did not. 
 I will, however, say that I loved how we saw so much more of Lily and that her role has definitely expanded. You'll see more of her history in Timepiece and she'll certainly help Kaleb out. (You have no idea how much I'd love to tell you more than that, but you'll just have to read to find out what I'm not telling you.) Em and Michael are also definitely present, but again, the focus is definitely more on Kaleb for obvious reasons. 
 As for the pacing, I think it was right on the mark. Again, not too slow and not too quick. Just enough action to balance out the romance (and character growth) as well as adding to the plot as a whole. Would I recommend Timepiece to you? If you've enjoyed Hourglass, then definitely! As for me? I'll be looking forward to Infinityglass next year.