"'It sounds as if it was like being in love.'" (1.151)
This is the boy's opinion of vampirism. He has a point. Love is one of those emotions that can be incredible and uplifting, but it can also be devastating and destructive. The same could be said of being a vampire.
"I felt some measure of love for Babette, though not the greatest love I've ever felt. It was foreshadowed in Babette." (1.261)
Louis is pretty blunt here calling his love for Babette foreshadowing. You can argue about whether his "greatest love" is Claudia or Armand, because both of them grow to hate Louis in their own way, just as Babette does. Or is Louis's "greatest love" both of them?
"We reeled about the room as if to the wildest waltz. Father and Daughter. Lover and Lover." (1.429)
You're allowed to be a little skeeved out by Claudia and Louis, because at times their relationship can be less family love and more… lover love. This time's an example: Louis compares them to lovers using those exact words.
"'I love you, Louis,' Claudia said over and over." (1.624)
Claudia says she loves Louis only after he dumps Lestat's body for her. Would she feel the same way if he refused to be an accomplice in her scheme?
"What I would not have given, as I watched her, to touch her silver hair, to whisper love to her, if love would not have loosed on her remaining years a horror worse than grief." (2.33)
Here is a rare instance of familial love. Louis tells us about how he watched his sister age and die. As a vampire, he could only watch from a distance, which makes his love all the more bittersweet. How does this compare to Louis's relationship with Claudia?
"I am not so much in love with happiness." (3.2)
This is an understatement. The self-hating Louis seems to be in love with pain. He loves to hate himself. Does he have a point, though? We're not sure how okay we'd be with all this vampirism stuff, either.
"'Love?' [Claudia] mused. 'What do you mean by love?'" (3.236)
We're not sure if Claudia is antagonizing Louis (as if she's asking him what he could possibly know about love), or if she really doesn't understand what love means. Maybe she does understand, but she's bitter about the fact that, stuck in a five-year-old's body, she'll never really have it. We'd be bitter, too.
"For vampires, physical love culminates and is satisfied with one thing, the kill." (3.275)
Here we see Louis telling us how vampires equate killing with love. Maybe they do love their victims? If a vampire loved us, we'd rather have a box of chocolates than a bite to the neck, fang you very much. We wonder, though, if this connection between sex and death is really limited to vampires. After all, the French call "culmination of physical love" a "little death." What do you think? Is sex just kind of violent or deadly in general? In a way?
"'Love?' I asked. 'There was love between you and the vampire who made you?
[...] "'Yes,' [Armand] said. 'A love so strong he couldn't allow me to grow old and die.' (3.425-3.426)
Louis is shocked to hear that Armand and his maker loved each other. Louis hates Lestat so much, he can't even imagine a world in which he might have loved the man.
"'Now I'll fight for you. Do you see how ruthless I am in love? Is this what you meant by love?'" (3.438)
Here we go again. We're wondering if Armand is being metaphoric, or if he really doesn't understand what love is. Because he's a really, really old vampire, we're not sure if the standard definitions of human emotions still apply to him. Armand may also be suggesting that Louis himself doesn't really understand love. What does Louis want, after all?