While I recommend that you educate yourself on trademark law rather than listening to anybody here (including me), the upshot is that it's a "mark of trade." You can't ever look like you're using another company's reputation to support your own venture. If "Blue Bolt" is trademarked or if the book has significant, current market penetration, then your prominent use of the name (titles, advertising, etc.) in a competing product is considered fraudulent.
As for other characters, I can only recommend reading around, because there's a lot of material that wasn't renewed. As long as you never, ever use a concept that originated (with the character, I mean) in a still-under-copyright work, it's in the public domain and therefore free to use.