There are many reservations about reading books in order to find out how to have intercourse, such as the following:
1. It may provoke desires in you that you cannot fulfil in any permissible way. This is a problem that is not farfetched, especially for one who does not have a wife to turn to.
2. Most of these books teach perverse forms of intercourse. Some of them go against the fitrah and sound human nature and others go against sharee'ah, such as anal intercourse.
3. Reading about these kinds of intercourse may put a man off his wife who does not do these kinds of actions well, and he may become attached to those things and the people who do them.
4. Reading these books may make you want to know more, and the devils among mankind and the jinn may lead you to read books which contain pictures, and you will end up doing something that is against sharee'ah.
5. Reading them encourages you to buy them, which helps to propagate them and encourages the printing of more editions.
6. There is no guarantee that these books will not fall into the hands of people who will be encouraged by them to do haraam actions. Your situation as one who wants to learn as a preparation for marriage is not like that of others who may get their hands on these books.
Moreover, Allaah has created in the male an inclination towards the female; having intercourse with a woman is not something complicated that needs a lot of explanation. A man will know what to do instinctively. If he needs any help the way to get this information is usually from the closest of people to him, or the most sincere among brothers who are already married. Hence there is no need for these books.
And there may be other reservations. Hence we do not think that you should read these kinds of books. That does not mean that you should not learn about the permissible way of having intercourse. But what we have mentioned is that you should not read what has been written by those who are far removed from Islam, good taste and a sound human nature.
You can read about married life and intercourse in the context of shar'i rulings and advice, that is free of the reservations we have referred to, on this site under the heading of Married life. This is in the category on Marriage.
And Allaah knows best.
Reproduced from Islam QA