bash switch-case statement gives syntax error

#!/bin/bash


echo "Title: "
read title
echo ""
until [ -n "$title" ]
do
    echo "Please enter title: "
    read title
    echo ""
done
echo "Author: "
read author
echo ""
until [ -n "$author" ]
do
    echo "Please enter author: "
    read author
    echo ""
done

check=cat ./BookDB.txt | egrep -ie "\b""$title""\b" | egrep -ie "\b""$author""\b"
if [ -z "$check" ]
then
    echo "Error! Book does not exist!"
    #need some code to continue
else
    echo "Book found!"
    all=cat ./BookDB.txt | grep -i "$title"

oldtitle=`echo "$all" | cut -d ":" -f1`
oldauthor=`echo "$all" | cut -d ":" -f2`
oldprice=`echo "$all" | cut -d ":" -f3`
oldavail=`echo "$all" | cut -d ":" -f4`
oldsold=`echo "$all" | cut -d ":" -f5`


fi
    while :
    do
     echo ""
        echo "  a) Update title"
        echo "  b) Update author"
        echo "  c) Update price"
        echo "  d) Update quantity available"
        echo "  e) Update quantity sold"
        echo "  f) Back to main menu"
        echo ""
        echo -n "Please enter your choice: "
        read option

    case $option in 
    a ) 
        echo -n "New title: "
        read newtitle
        if [ "$oldtitle" = "$newtitle" ]
        then
        echo "Title is the same as original"
        else
        all_title=`cut -f 1 -d ":" ./BookDB.txt`
        check=`echo "$all_title" | grep -i "\b""$newtitle""\b"`
        fi
            if [ -n "$check" ]
            then
            echo "Book title already exists."
            else
            sed -i "s/$oldtitle:/$newtitle:/g" ./BookDB.txt
            echo "Book title successfully updated."

        fi

b ) 


esac
done

i can't run this code on bash. they say there is a syntax error at my CASE selection at this line b )

which i see no problem at all