A reading journal can preserve a conversation with a book without becoming a second writing project. Start with its title, author and the date you read it. Add the edition or translator when that information matters to your notes.
Write one observation in your own words. It might concern a character, an argument or an image that stayed with you. If you copy a short passage, mark it clearly as a quotation and record its page.
Leave space for questions rather than forcing a final judgement. Your response may change after a discussion or a later reading. A useful notebook lets those changes remain visible.
Return to earlier entries before choosing your next book. You may discover an interest you want to follow or a question worth revisiting. Keep the format simple enough that opening the journal feels inviting rather than like catching up on unfinished work.