How can I extract essential information from a book in as little time as possible?

Sometimes you need to read several books for an essay and it is difficult to read them all without waisting some precious time you could spend planning your essay or writing it. Reading should not take more than 3 hours. What you want to do is read the introduction and conclusion fully to be able to seize the main ideas and arguments of the author. After that, you should look for the chapters which titles seem relevant to the essay question that you are trying to answer. Once you have read those, read the first line of each paragraph in the remaining chapters. If the book is well written, the main argument will be expressed in the first sentence of each paragraph and there is no need to read the rest unless you find it important for your essay. This technique works very well for me doing a history degree at university.