SOLVED. YA/ Adult Fantay . Set in a society of rats, each gets given a job. Main character rat chooses differently. Ruled over by conjoined Rat King. [s]

[Ali]

Set in a Victorian'esque society of rats, where each gets given a job to do. Some are fighters, some are knowledge keepers etc. Main character female rat decides she wants a different job and makes enemies of 'evil' rats. Reigned over by Rat King (conjoined multi rats). Also the story is about the humans living above in the seedy underbelly of the city, especially the rat catchers, trying to catch the rats for dog baiting competitions.
The female rat meets some nice human children that try to help.
Read at least 6 years ago.

[Ali]

Sorry, thats not it.

[Ali]

Found it - The Twyning, by Terence Blacker!!

[Kris]

Glad you found your book, Ali. Here's the link - The Twyning by Terence Blacker.