Even though you can’t recall the plot or content, that book you read still matters. Follow the link above to get some real research on how the books you read make up a big part of you, even if you can’t remember them. James Collins says:
…it makes in intuitive sense: we have been formed by an accretion of experiences, only a small number of which we can readily recall.
Read the article, but don’t worry about remembering it.