@hakan42 - I just tried exactly your described scenario and it worked perfectly fine for me. I did the following:
Created an empty book with title "Dark Imperium", author "Unknown"
Set the goodreads id to goodreads:588334
In the Edit Metadata->Configure download metadata screen, had only the Goodreads plugin enabled, with all fields to download checked.
Clicked the Download metadata buton
Code:
Starting download
Query: title:Dark Imperium; authors:Unknown; goodreads:588334
Running identify query with parameters:
{u'authors': None, u'identifiers': {u'goodreads': u'588334'}, u'timeout': 30, u'title': u'Dark Imperium'}
Using plugins: Goodreads
The log from individual plugins is below
****************************** Goodreads ******************************
Request extra headers: [('User-agent', 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/525.19 (KHTML, like Gecko) Chrome/0.2.153.1 Safari/525.19')]
Found 1 results
Downloading from Goodreads took 1.53900003433
---
Title : Dark Imperium (Warhammer 40,000 Novels (Warhammer 40,000)
Author(s) : Marc Gascoigne & Andy Jones
Publisher : Games Workshop
Rating : 3.17
Published : 2001-01-30T00:00:00+00:00
Identifiers : isbn:9780743411622, goodreads:588334
Comments :
In the war-torn 41st millennium humanity stands on the shores of damnation, their only saviour is the Immortal God Emperor and the massed armies of the Imperium, in this searing anthology of Warhammer 40,000 stories torn from the pages of Inferno! magazine.
Goodreads book url: u'http://www.goodreads.com/book/show/588334'
********************************************************************************
The identify phase took 1.60 seconds
The longest time (1.539000) was taken by: Goodreads
Merging results from different sources and finding earliest publication dates
We have 1 merged results, merging took: 0.00 seconds
As you can see it found and parsed the result.
I am running with the latest Calibre source code, though with only one plugin enabled the changes Kovid has made should not make a difference