Read Traveller and Battletech. It's more setting books/wikis than novels so it's easy to get through fast but frankly this means you're probably having massive tape banks and ENORMOUS transmission dishes on your mail carrier ships to pump out data ASAP. Probably a fleet of overdressed and underpaid operator girls to run the whole spiel too.

On the political/economic/social side things don't change TOO much. When you have fast travel but not fast comms you want to look at it as a language barrier over a distance barrier almost. Lots of cultural misunderstandings and insular idiosyncrasies that have to be negotiated and navigated because culture comes in large blocks akin to how we used to get travel accounts, diplomatic missives, translated folk tales and newspaper reports from distant lands.

Corporations will likely be closer to semi-governments. What made the east india trading company so powerful was in part that it HAD to be so powerful in order for achieve its aims via having enough political and military muscle in any given part of its structure to keep doing what it did independently.

Governors might be appointed rather than elected and told to not be *too* involved so the government below them can do the actual work while they respond to things the peeps back home want done.

Just some vague off the cuff ideas.