do you use books or free resources?

hey everyone,

i'm starting to study for the GRE, i graduated with a masters but didn't need it to get into my program. i'm planning on applying to phd programs a year or two out want to give myself ample time to study and retake if necessary. i was just curious on how many people use books vs free resources? i feel like there are so many free resources out there, i'm debating shelling out money to buy the book.