cbwjm
Seb-wejem
Although not the novels, there is a wealth of information about Ravnica on the MtG website about Ravnica. Normally, when looking up the worlds of MtG, I type "site:https://magic.wizards.com planeswalker's guide to" into Google to see what comes up, below is one of the of the articles about Ravnica, it has a guild selection that takes you to the different guilds providing information about their structure and beliefes. There are likely to be a number of other articles about the plane around as well. These provide a lot of information about the 10 guilds of Ravnica at the time of the Return to Ravnica block.
https://magic.wizards.com/en/articles/archive/planeswalkers-guide-gatecrash-part-1-2012-12-05
https://magic.wizards.com/en/articles/archive/planeswalkers-guide-gatecrash-part-1-2012-12-05