This might sound like a no-brainer, but this is something I've learned in writing speeches. The best way to do it is to come up with the main points (discussing the three books that have influenced you) for the body of your work: in other words, "Say it." Then, simply go back and introduce your work by giving a sneak preview of your main points ("Say what you are going to say") and wrap it all up by concluding and reviewing your work by, again, touching upon your main points ("Say what you have just said.")
Again, that mind sound simple, but it might help, for the most important thing to do is write. Once you have written enough and have molded your thoughts into the main part of your essay, the introduction and conclusion will be the easy parts.
Ned Plimpton