Don't know how to GROUP_BY my data - mysql

Question

Here is a description of my tables
describe book;
+----------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------------+-------------+------+-----+---------+-------+
| isbn | varchar(20) | NO | PRI | NULL | |
| title | varchar(30) | YES | | NULL | |
| date_published | date | YES | | NULL | |
| publisher_id | int(11) | YES | | NULL | |
+----------------+-------------+------+-----+---------+-------+
describe author;
+------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+-------+
| author_id | int(11) | NO | PRI | NULL | |
| first_name | varchar(20) | YES | | NULL | |
| last_name | varchar(20) | YES | | NULL | |
+------------+-------------+------+-----+---------+-------+
describe stored_on;
+--------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-------------+------+-----+---------+-------+
| isbn | varchar(20) | YES | | NULL | |
| total_copies | int(11) | YES | | NULL | |
| shelf_number | int(11) | YES | | NULL | |
| library | varchar(20) | YES | MUL | NULL | |
+--------------+-------------+------+-----+---------+-------+
describe written_by;
+-----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+-------+
| isbn | varchar(20) | YES | MUL | NULL | |
| author_id | int(11) | YES | MUL | NULL | |
+-----------+-------------+------+-----+---------+-------+
I am trying to display book name, list of authors that wrote that book, shelf number, total copies, and the library the book is located at.
SELECT
b.title,
GROUP_CONCAT(CONCAT_WS(' ',a.first_name, a.last_name )) AS authors,
so.shelf_number,
so.total_copies,
so.library
FROM
stored_on so
LEFT OUTER JOIN book b ON so.isbn = b.isbn
LEFT OUTER JOIN written_by wb ON wb.isbn = so.isbn
LEFT OUTER JOIN author a ON wb.author_id = a.author_id
GROUP BY (b.title);
I don't know how to group my data at the end in a way that will give me duplicate titles/isbn.
Example: There is a book at one library, and the same book at another library, I want to print out the data for each one. They are all listed in my stored_on table to begin with, and I can print out all of the entries when I don't use GROUP_CONCAT, but I do get double entries in the authors field.
Cannot seem to figure this one out.