There is a book called The Secret Service of Harry Potter 7+ 1, which was written by fans. There are also some related materials, such as the function of potions, which fans summarized from books, which may be of some use to you!

Where to buy it is not clear! You can go to shopping websites like Taobao.

Here are some headlines written by fans. Search online, there may be books you want.

Ha fans wrote:

Seven conjectures of Kazakhstan

Play with Harry Potter

Harry Potter fan handbook

Rowling's biography

Wings of Dreams-My Harry Potter

The true story of Harry Potter and me

The wizarding world of Harry Potter

A magician's companion.

Department of mysterious affairs

The magic book of the great wizard

Harry Potter and Platform 9 3/4

I like Harry very much.

Complete Works of Harry Potter (Muggle Required Reading)

Harry Potter-Secret Documents

A letter to Harry Potter

Harry Potter-Muggle School of Magic

Magic princess Emma

Magic little prince

Harry Potter Encyclopedia (Xinxing Publishing House)

Harry Potter and the Department of Mysteries (I'm talking about this one! )

Harry Potter and the Wizard Archives

Read Harry Potter's Growth Code

If you want to buy these books, but the bookstore in your city doesn't sell them, you might as well buy them online. I suggest you go to Zhuo Yue, Dangdang and other well-known large-scale online shopping malls, look for genuine products, and beware of being deceived. )

Give me the best.