This is a simple .07mm thick book mark. The pumpkin head is slightly thicker and below has a ridge so it doesn't fully slide into the book. 

I printed mine in PETG and it has a nice flex to it, but I'm sure any filament will work for this. I printed mine at .20, so anything  lower you'll get much better results.

I stopped the print for the last 2 layers to do a dual color book mark.

Enjoy!