I am trying to get this file to show Author before the CSV which is the "," only the first name shows

#!/bin/bash
# this is the input
#Clive Cussler,Ghost Ship,9780399167315
#Clive Cussler,Bootlegger,9780399167295
#James Patterson,Invisible,9780316405345
#James Patterson,Gone for Now,9781455515845
#James Rollins,Map of Bones,9780062017855
#Michael Connely,Lincoln Lawyer,9781455516345
#David Baldacci,The Escape,9781478984345
set INPUT=0

set IFS=,

    

echo 'how do you want to sort the file?'
echo '1 for Author'
echo '2 for Title'
echo '3 ISBN'
read -r INPUT

case $INPUT in

        1) sort -t "," -k 1 project2.input > Proj2.sorted;
           outfile=project2.author.out;;

        2) sort -t, -k  project2.input > Proj2.sorted;
           outfile=project2.title.out;;


        3) sort -t, -k  project2.input > Proj2.sorted;
           outfile=project2.isbn.out;;

        *) echo 'invaled not 1-3'; exit;;

esac

# Setting up echo and header information here.
echo "******************************************" > "$outfile"
echo "* CIS 129 Project 2                      *" >> "$outfile"
echo "*          6/19/2021                     *" >> "$outfile"
echo "******************************************" >> "$outfile"



while read -r author title isbn
do
       echo $author

done < Proj2.sorted

The bash shell's set command is not the one you want in this context - it is used for setting the value of shell options and positional parameters.

Specifically, the command set INPUT=0 sets the value of the shell's first positional parameter, $1, to INPUT=0. Then set IFS=, replaces it with IFS=,. The correct assignments would simply be INPUT=0 and IFS=, respectively.

HOWEVER, the only place that the value of IFS appears to be significant is in your read command - and there you can set it locally i.e.

while IFS=, read -r author title isbn

so you don't need to set IFS=, elsewhere. You should also get into the habit of quoting variable expansions. So

while IFS=, read -r author title isbn
do
       echo "$author"

done < Proj2.sorted