Tense is one thing that influences a writing style and therefore the whole book. It comes in a variety of flavors from first to third. I choose first person tense because I want the reader to feel like they are there in the present, seeing the world through the eyes of my character as he or she sees things.
Choosing your tense is choosing your point of view. First person is a tense that is pretty much seen through the eyes of the character the author is inhabiting. I started writing my series of books in it and have not really strayed from this style as of yet. Maybe when I go backwards and start writing the historical part of my fictional world, things will change, but for now its all seen though the eyes of the person speaking the dialogue when there is talking. Outside of dialogue, first person reminds me of the voice speaking out of the clouds in "The Waltons", a show I seem to be remembering more and more for some strange reason.
It does have its limits though, as critics are quick to point out. To sty in first person means you can't really talk about things the character can not see, which I am OK with for the most part. My all time favorite authors James B. Parker and Roger Crais put their characters in the drivers seat and speak/write in a first person tense. Spencer and Hawk and Elvis and Pike would not be the characters they are if they were in third person.