Maxim is very much a hero in the Byronic mold. That is to say that he stands apart from human society, cold and unapproachable, dashingly handsome, but with something dark and brooding about him. That we only come to know him through the eyes of the second Mrs. De Winter merely accentuates his distance from us.
But as with Mr. Rochester in Jane Eyre, we sense something else lurking beneath Maxim's harsh exterior. There's a war raging inside that tortured mind of his, between competing impulses of good and bad. At times he can be quite extraordinarily cruel and bad-tempered. At other times, he can be surprisingly thoughtful and kind, as when he travels to France with the second Mrs. De Winter, for example.
But whether married or not, Maxim is destined to remain a lonely figure. He stands apart from the rest of humanity, living in a world of his own. That world is Manderley; and Manderley is everything to Maxim. Like a true Gothic hero, his isolation and estrangement from the world follow a fall from grace. And that fall was related to his obsession with preserving Manderley and everything it represents. Outside of that self-contained world, Maxim cannot exist in the fullest sense of the word. To live among other people he must present a mask, a mask of a man aloof and in control. The real Maxim, however, is more complex, someone we can never completely know, even after the revelation of his deepest, darkest secrets.