Could write a book illiterate person? In principle, yes, but hardly some of the publishers want to take this book. And a man reading a book, can not understand what is meant by its text, because literacy - the key to understanding.
Reading
Man, never keep a good book in hand, is unlikely to create something worthwhile itself. Therefore, reading, education is important for writing the book. When reading the books in my head laid some standards, samples of style; remembered interesting turns of phrase. Reading books and helps in the formation of literacy.
Experience
What can write people, who saw in his life only the gray walls of his apartment? That's right, nothing. To write a book that will be interesting to read, the writer must have a certain experience. To replenish the "piggy bank" impressions useful to travel, meet new people, explore different activities.
Idea
When you sit down to write a book, you should have an idea you want to convey to the readers. It does not have to be a fundamental philosophical question, like the search for meaning in life. Guiding idea of the book can be anything.
Logic
When you write a book, you need, among other things, skills, logical construction of the text. If your phrase fall "from the ceiling", and from the well-known truth be something incredible, the reader will not understand. Learn to build the text so that it is clearly visible a certain logical structure.
Publishing house
Finally, when the book is ready, you need to find a publisher who agrees to read it and possibly publish. However, if you write "on the table" or for a narrow range of readers, this problem will not worry you.