Black has a lot of options against the Catalan, and they can lead to very different types of game. There is no generally agreed 'equalising' or 'clearly best' line for Black (which is why the Catalan is popular with the strongest players), but several of Black's options require specific concrete knowledge from White (which is why it isn't so popular with the masses). As with many other openings, some knowledge and experience on your part will usually pay dividends against opponents with less.

For an introductory book, I would suggest The Catalan: Move by Move (Everyman, 2017) by Neil McDonald. Neil is usually very good at judging the level of detail amateur players want and need, and this book is no exception.