Hi mago78,
are you talking about a view in the frontend or backend? Send me the link or a print screen.

Ok, I understand!
Edit the file <your_site>/component/com_abook/models/category.php and change the row 65
from
$query = "SELECT a.*, GROUP_CONCAT(bb.name SEPARATOR ', ') AS author, "to
$query = "SELECT a.*, GROUP_CONCAT(bb.name ORDER BY bb.name ASC SEPARATOR ', ') AS author, "
edit the file <your_site>/component/com_abook/models/book.php and change the row 136
from
' WHERE b.idbook = '. (int) $this->_id ;to
' WHERE b.idbook = '. (int) $this->_id .
' ORDER BY author ASC ';
edit the file <your_site>/component/com_abook/models/search.php and change the row 129
from
$query = " SELECT a.*, a.title AS booktitle, cat.title AS cattitle, GROUP_CONCAT(bb.name SEPARATOR ', ') AS author,  "to
$query = " SELECT a.*, a.title AS booktitle, cat.title AS cattitle, GROUP_CONCAT(bb.name ORDER BY bb.name ASC SEPARATOR ', ') AS author,  "
This fix will be included in next version.