I am 13 years old, yesterday I got a key stage three science book and as soon I opened the book, it shows you about growth and how humans develop, and it tell you what happens to boys and girls at the age of puberty and how babies come. So it is really sex education. Should I read it or skip the page? I have not started yet; I just took a quick glance. Please respond quickly.

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Studying such books is permissible for the specialists in medicine, or those who are in need of this knowledge. But others, like you, are not permitted to look into such books even if there are no pictures. The reason is that they excite one sexually and lead him/her to sexual fantasies. Know that such books, in fact, do not benefit you, but harm you.
The Prophet (Sallallahu Alaihi wa Sallam) said: "Cherish that which gives you benefit" . [Reported by Imam Muslim ].
Know that studying to increase sexual knowledge or to know how a husband has sex with his wife is not a sound reason, since a human being naturally knows such matters.
Allah knows best.