Unable to replace Special character using Sed Command

Question

I have to replace word Check with protected/note/run.json from book.txt file but I am receiving error.

sed -i 's/Check/protected/note/run.json/g' book.txt
Error: sed: -e expression #1, char 24: unknown option to `s'

Can someone please let me how to replace Check with protected/note/run.json.