Personal opinions about them

 

Lucius appears since the second book, Chamber of Secrets, and Narcissa since the fourt one, The Goblet of Fire.
Their relation isn't explained, so we can think what we eant about their intimacy.
They'are husband and wife, but their relation isn't just a bond between two persons that share a son or two lovers, they share the respect for a tradition that see the pure-blood magician as the only ones that deserve to live in the magic world and that can use magic. Tthey're totally devoted to Lord Voldemort and their marriage isn't totally pure and surely didn't make for love, but reading book by book we can understand the real feelings of Lucius and Narcissa, because there's a reason for anything and they share a son that they love, so even if in darkness, their solder is solid and they're the prestigious Malfoy Family, that hide the love for the other one in the bottom of the heart. Pride and honor are the peculiar caracteristics of them, but it's unchallenged that Narcissa and Lucius feel reciprocally the same thing.

This is one of the reason why I love them the most. They're "the imperfection of the perfection" but they prove that everyone, in his heart, can love the other one in a lot of ways, because love is a feeling that lives in every heart, good or evil that it could be.