A friend and I exchange manuscripts from time to time, and her latest is, to use an overused word that actually applies here, riveting. That got me thinking about pacing.
Sometimes a book reaches out and grabs you by the throat and won't let go. You need to know what happens to the protag, need to know why he/she's in such deep trouble, need to have the whole story. You hear people say they stayed up half the night to finish a book, and it's understandable. You become so involved with the characters that their outcome matters, and you can't let them down by making them wait while you sleep, or cook, or go to the dentist.
The problem with great pacing is that the author sets herself up somewhat. The result had better be worth all that adrenalin, because the reader is so involved. While we may read a gentler mystery and think, "That was nice" when we're done, we can't accept nice when the author sets the excitement level at full from page one. That explanation had better be good.
We've all read thrillers where the energy wanes at the end. We've all been, well, thrilled by thrillers where the author is able to deliver on the promise of Chapter One. I haven't finished my friend's story yet, so I can't say if she achieves her end, but I admire her for setting the bar so high. And I wish I knew how she did it.