You, of course, want an answer of "Yes"--even better, "Yes!" Assuming you have done your homework, you have already selected a topic which you feel readers will want to explore. Your task in the introduction is to provide enough context and content for readers to sell themselves on your work.
A good introduction provides the reader with two crucial pieces of information. It presents a topic in which the reader will presumably be interested, and it presents the overarching theme of how that topic will be explored. This theme will determine what implicit or explicit questions the book will answer, which viewpoints and ideas will be emphasized, and much of how the book will be structured as it develops the theme to a reasonable or satisfying conclusion. A book written with the aim of portraying a successful racehorse as an animal that overcame numerous obstacles to become a popular champion and a book written to portray the success and popularity of that same racehorse as emblematic of an ongoing class struggle in the time period and society in which the horse was running have the same subject, but their differing themes will result in two very different books.
Because of its importance to the book's purpose and overall development, failure to develop a clear concept in your own mind of what your theme is will almost certainly doom your book before it is ever written. It has often been said that if you can't explain an idea in a way that an intelligent ten-year-old can grasp, you probably don't understand it yourself as well as you think you do. If you can present your theme to a naive listener---one who knows little or nothing about the topic you want to explore---and have that person respond with a genuine "That sounds interesting!", then you are probably on the right track. A confused look means you'd probably better go back to the drawing board and figure out both exactly what it is you want to say and how to say it.
That being said, another pitfall to avoid is trying to do too much during the introduction. Your intro is the place to present your topic and main theme in a focused, readable manner that invites the reader to want to learn more. It is not the place for a complete outline of the work, an information dump, or a discussion of why you chose to write it as you did. A good rule of thumb to follow: any kind of supporting information that can be placed in a later chapter or part of the book probably should be. You don't want to give so much information in the intro that the reader has no reason to read the rest of the book!
In conclusion, think of a book introduction as parallel to beginning an interview with a potential employer. You want that reader to hire you (buy your book) as a source of information or entertainment. Keep your intro focused on what it is you have to offer that you believe will meet the reader's wants or needs in a fresh, interesting way, and you'll be on your way to drawing them further in to the story you want to tell.