The adjective can imply endearment when describing someone's personality, often positive. His bookish demeanor has always drawn me to him.
Pro Tip 2/3
Non-Social
Use 'bookish' to suggest someone may prefer books to social events without being negative. She turned down the invitation, content with her bookish evening plans.
Pro Tip 3/3
Personality Hint
The word can give clues to a character trait, like being introverted. He's the bookish type, often lost in thought.