Loads of ways to look at that.
First there's the format. People use books, PGN files, Fritz trainers, chessable, etc. I personally prefer using PGN files of books, because I find it to be the best of both worlds.
Second is the difficulty of the particular book itself. Play the French is meant for quite strong players. I took a look through it before and it was too much for me too. A much better book in that regard for example is "first steps e4 e5" by John Emms. Gives a defence against 1.e4 whilst also teaching good basics about chess.
Then there's the argument about whether opening books are a sensible thing to be looking at before being quite a strong player. I think they probably are when they come in a games format rather than just a phone directory of lines. More important are things like endgames though.
So what do you do when you study an opening book?