Here is a list of all the Sweet Valley series. I have also put in a recommended age on which to read them. 

Sweet Valley Kids: The twins are 7 years old and the books have big letters.

Suitable for Kids aged 5 - 8

Sweet Valley Twins: Jessica and Elizabeth are 12 years old.

Suitable for children aged 9 - 13

The Unicorns club: Is about the coolest girls in the school. The unicorns.

Suitable for children aged 9 - 13

Sweet Valley High: Jess and Liz are 16 years old. They study at High School; all titles consist of several words.

In the cover they say that this series is for ages 12+.  I started reading them younger then twelve and they are too hard to understand and have some unsuitable themes in them. I personally recommend these books for ages 12 - 16

Sweet Valley High TV: These books are fetched from the TV-show. On the front page there are photos. 

 Suitable for teens 12 16

Sweet Valley Senior Year: These books follow on from Sweet Valley high as the publisher is discontinuing all Sweet Valley books but these.  There is an earthquake and several characters are dead.

Suitable for teens 13 - 16

The Twins in Sweet Valley: Elisabeth and Jessica are 16 years, but the books are a little bit different. It isnt about school; instead they can for example be visiting Britain.

13 - 16

Sweet Valley University: Jessica & Elisabeth Wakefield are 18-years old. Read about how their lives in SVU.

Suitable for teens 15 19 older people may still enjoy them.

* You can make your own Sweet Valley Site and we will advertise it for you! Click on the link above!