So you've finished the first chapter of your book and made sure to open your story with either a bang or a captivating introduction to the tale. You've given the reader something to be interested in; however, now it's your job to create some sort of investment. If the reader isn't invested in the story, chances are they might not even finish reading your book. This is where pacing comes in to play. In many ways, it's analogous to both first time and subsequent kisses.
A story's pacing is the fabric that weaves together character and plot development. Without pacing, heroes stagnate, villains become boring, and the entire story falls apart. Why? Because the reader will get bored wading through all of that exposition and meaningless dialogue that does nothing to advance the story. It's no different than exchanging a first kiss with someone with whom you realize (perhaps even instantly) there is no chemistry. The kiss is awkward, dull, and so painfully slow that you just can wait to disengage and find a polite way to say goodnight. A proper first kiss is tantalizing and subtly implies that there are even more exciting things down the road. The question then, of course, what is that road like?
There are many types of first kisses that fulfill the dual promises of excitement and foreshadowing, and the same is true of pacing. Some stories require a hot and fast pace, while others demand a sort of slow burn. To some extent, your characters, and their impact on the plot, will affect your story's pace. Additionally, you'll need to have a good sense of the type of person you believe will read your story. Employing a slow burn style of pacing may work for some, but not all readers. Alternatively, others may be turned off by a plot that moves at break neck speeds if the reader feels like character/story development was sacrificed.
As a writer, you have to remember that you are exchanging a very personal and intimate part of yourself with a total stranger. Your book is the first date. The pacing of your book is the first kiss that determines whether there will be another date (i.e. your readers pick up your sequel, series, etc.).