SOLVED. YA Fantasy unique cover that opens from center. [s]

[Colby]

I'm looking for a book published before 2005/2006. The cover of this book is super unique in that it opens from the center of the book, rather than the side.

The details I can remember:
Fantasy, crossworld genre; children's lit or YA
The main character uses he/him pronouns
The main character has a bug catching net and a journal, I think?
It takes place in summer?
He's wandering in a forest and stumbles upon a portal to a different world with magical creatures- the title of the book and this world has something to do with "middle" or "in between," hence why the book opens from the center of the front cover

I read this book in middle school and found it in my school library. It's driving me nuts that I can't remember the title or find it in my Google searches. Do you know which book this is? Thanks in advance!

[Joseph]

Some versions of The Divide, by Elizabeth Kay did this.
You can see the cover image here: https://www.publishersweekly.com/978-...

[Colby]

Yes! This is it! Thank you so much!

[Joseph]

Glad to help!