As soon as a new book comes to my hand. I always read the preface first and then the table of contents. If it happens to be a thin one, I often finish reading it at one sitting. Otherwise. I often browse through one or two chapters or sections before putting it onto my bookshelf. I seldom read a thick book from cover to cover unless it is a novel. By dint of the first impression it made on me at the time of buying. I have a rough idea of what the book is about and what useful materials in it are available to me. But I have little idea which book is to be read or looked over again at what time. It is completely subject to the whims of the moment.