Just what is pacing. I've thought about this a lot ever since a writer friend told others that my book Obsessions showed a mastery of pacing. Now this is a medical suspense so pacing was an interesting effort. Pacing has to do with the flow of a story. If you've ever read a book when you wanted the writer to speed up or to slow down, either condition is part of pacing.
Pacing can be tricky. When doing an acion scene, short sentences are better than long ones. Keeping the description tight can help a scene flow faster. One thing is not to keep up the rapid fire writing for too long or your reader amy be out of breath.
Long sentences full of phrases and clauses slow the pace. This gives a reader time to savor the story but continued for too long, this can make the reader want to fall asleep.
Pacing in ensemble stories can be useful. I do a lot of these and some that are essentially two view point characters. Even switching from one character to another can slow or speed up the pace according to the intent of a scene.
Pacing is also a devise that can pull a reader to turn the page. Ending on a note that causes curiosity can pull a reader to the next chapter.