While we aren't necessarily experts on guiding people to the best texts about sex, we do know that you can be a great source of knowledge and support when it comes to sexual activity for a teenager. As a teen, your son is going to be facing social and media pressure to be sexually active. You could put your son in a great position to resist these pressures by helping him understand what sexual intercourse is, what the risks are, and what the benefits of waiting are.
While we encourage abstinence, you would probably find it beneficial to describe the methods of sexual prevention to your son as well- what condoms are, what birth control is, etc. At the same time, remind him that these materials only decrease the chances of pregnancy or sexually transmitted infections- they do not totally eliminate the risk.
Remember, you can be an advocate and source of information for you son, and that is a really good position to be in as a parent.