EPNS Baslet B&O mark then a star then "S"

I recently bought a silver basket at a car boot sale for 50p and have just sold it for £550 and now I’m addicted! (I know this is a once in a lifetime thing, but it’s peaked my interest in silver etc.)

I’ve got a EPNS basket with a B&O stamp - then a star - then “S”

I’ve had a bit of a search on the internet but couldn’t find anything. Can anyone recommend what books should I get to help me get more information on this massive area of silver/EPNS etc, or indeed tell me more about the basket.

Many thanks