this is really stupid but i have no idea how to respond to this message??sorry?

[esssee]

id like to apologize for how pathetic and awkward this is but

i received a message from someone i mutually follow (but haven't met in real life) on a social networking site and im not sure how to reply because i dont normally get messages like this?anyway it went something like:

hello, I see you like (insert some book series here), i do too so we should be friends?

how should i reply?i wouldn't mind talking to them a bit more but like i've said im not sure how to respond?

once again i apologize for how stupid and awkward this is.
also im sorry if i put this in the wrong section!
I know it's not a scam or fake because they regularly post updates and pictures.