I saw the semantics as this way; "comics" includes "comic strips" and "comic books", while "comic books" more specifically refers to properties that started in comic books. Analogy; when I say "the Americas", that includes both South America and North America, but "North America" specifically refers to, well, North America. As far as properties that started outside of comic books that have had adaptations, I draw the analogy with the word "African"; when I hear that word, I think of Nelson Mandela prior to thinking of Charlize Theron, Wilbur Smith, Louis Hayward, et al. If I wanted to refer to the latter group, I would say "an Afrikaans" or a "British descended African". (What about America? Well, they did not call it "America" till about 1492 or so anyway.)