best self help books relationships

What are some other good books out about relationships?

I just finished reading Men are from Mars, Women are from Venus. I absolutely loved it.
It is a self-improvement book, and I plan to read a few others by that author.
I’m open for any suggestions. They do not have to be self-improvement.
They can be fiction or non-fiction.
I am a teenager, so I would rather nothing too complex.
Any good book that deal with relationships, preferably between a boyfriend and girlfriend

“I Kissed Dating Goodbye” by Joshua Harris (it’s a real fun read. Trust me!)

“Boy Meets Girl” by Joshua Harris

Salmansohn Brings Humor to the Self-Help World