Why is Dracula written in the form of letters and diary entries?

Well, I think its written in letters etc, because it gives a sense of reality, after all it is a book about vampires, werewolves and based around a gothic genre. I mean if you ask me, I don't really believe in that stuff, but the book does however give the reader a sense of suspension of disbelief. This basically means that even though the reader may not believe in what's happening in reality, they suspend this thought and believe it, giving them a sense of adventure. Its almost like watching a James Bond movie, where James Bond literally NEVER DIES, sometimes people like to watch the film and believe that everything that happens is amazing and supercool, whereas some people (like me) think what the hell is going on? He would never survive jumping off a 50 story building after going through a fire blazing car crash? Its like that's just ridiculous. On the other hand, its adventurous and exciting to watch it without these thoughts in your mind.

The invasion of privacy throughout the novel is another thing that makes us want to read further, having the diary entries of two peoples conversation in front of us makes us want to find out more about the secrets, this way we can interpret the characters and the drama from a different aspect, its almost as if the reader is meant to be a third character, this is what makes it exciting, this is what suspends our disbelief!