"Set NBT text tag ??? of ??? to ???" doesn't seem to work on 'written books'.

Hello,

     Somebody suggested that I put in a bug report for my mod as to WHY the green GUI puzzle piece, "Set NBT text tag ??? of ??? to ???" is not working. I am attempting to use that tag to write text to 'written books', but no matter what data I use to replace the '???'s, it doesn't seem to work and all my books in my mod STILL say, "*Invalid book tag*" in them. 

     I have the first '???' set to the string, "pages", the second '???' is the 'written book' that I am trying to write to, and the third '???' is set to the string, "['{"text":"Minecraft Tools book"}'],title:Scriptures,author:"Michael S. Lowe",display:{Lore:["Scriptures"]}".

     If it is because the third ??? needs to be a type JSon and not a type string, how do I create JSons in the GUI structure? If it helps, I used, "Set NBT text tag(...)" and then "print(get NBT text tag(...))" on the next line, and the data I assigned DOES get printed... but the books (when testing out my mod) STILL say, "Invalid book tag." in them.