7th Sea is a very lore heavy setting and thus players will need to do their homework prior to starting the campaign. Most of the books have been out of print for a decade so your best bet for getting books is via pdf at places like DriveThruRPG. I can also loan out my hardcopies if requested.
At minimum each player will need to read the Player’s Guide and then once you’ve chosen a nationality you should read the nation book for your hero. If you belong to a secret society you may also read the corresponding secret society book.
If you are really interested you may read more nation books but not more secret society books. The Church of the Prophets book is open to read if you’re so inclined.
Players should never read the following due to lore spoilers:
- The GM’s guide
- The Game Master section of any Nation or Secret Society books.
- The metaplot books (Waves of Blood, Montaigne Revolution, Rapier’s Edge)
- Nation books outside of Theah (Crescent Empire, Cathay, The Midnight Archipelago)