Most Helpful Guy
Situation A; Pay him a non-romantic compliement; say he has good taste in books, or something like that, that won't get eeryone else in the group buzzing with gossip right away. If the guy is bright, he'll know what you really are saying.l
Situation B: Ask him what he's reading, if applicable. This is a safe, neutral way to see if he will engage with you
Or, if you want to do something bolder, ask him what he is thinking about right now This should get a laugh, and he'll know that it's a question asked by someone interested in him romantically.