Joe's a pretty interesting guy in that he's kind of gruff and rough around the edges, but he's also a big softie when it comes to Holly and he offers her (dare we say it?) a sense of unconditional love. The novel opens with Joe and he reappears at the very end when Holly is preparing to leave New York. It's Joe who jumps into action when Holly gets arrested, Joe who worries about what will happen to her if she gets caught trying to leave the country, and even Joe who arranges to have a limo take Holly to the airport even though he thinks she's making a huge mistake. And the final good-bye between Joe and Holly is one of the sweetest moments in the whole story. After surprising her with the limo, he struggles to hand her a bouquet of flowers or to look her in the eye:
"Kind, dear Mr. Bell. Look at me, sir." He wouldn't. He wrenched the flowers from the vase and thrust them at her; they missed their mark, scattered on the floor. "Good-bye," he said; and, as though he were going to vomit, scurried to the men's room. (18.9-18.10)
OK, the vomit part might not be that sweet (but it kind of is since it shows us how upset he is), but Joe sees something in Holly that compels him to love her no matter what she does, which makes him a pretty rare bird when it comes to the men in her life. He wants nothing from her, which we can't say for most of the other characters, and this makes us really, really like him.