[Dompie]

For testing purpose, I have collected a few more cover problems for you (not including the entire logging):

Running identify query with parameters:
{u'authors': [u'Neal Bascomb'], u'identifiers': {u'isbn': u'9789048833351'}, u'title': u'De wintervesting', u'timeout': 30}
Using plugins: BOL_NL (4, 5, 2)

Running identify query with parameters:
{u'title': u'Het gewicht van inkt', u'identifiers': {}, u'authors': [u'Rachel Kadish'], u'timeout': 30}
Using plugins: BOL_NL (4, 5, 2)

Running identify query with parameters:
{u'authors': [u'Noud Bles'], u'timeout': 30, u'identifiers': {}, u'title': u'Bevrijdingsvuur'}
Using plugins: BOL_NL (4, 5, 2)

Running identify query with parameters:
{u'timeout': 30, u'title': u'Zwemmen in het donker', u'authors': [u'Tomasz Jedrowski'], u'identifiers': {}}
Using plugins: BOL_NL (4, 5, 2)

All four books have a cover on the Bol site and the most important part of your plugin performs perfect!!!!

Edit: a fourth book added