"Favourite Romance book"
First thing that comes to mind for me is LJ Smith's Night World series. Another series I loved as a teen and still read over and over again. The Night World was a secret society of vampires, witches and shapeshifers with two rules: Don't Tell Humans and Never Fall In Love with a human. The books were of course all about humans who found out about the Night World and fell in love with a supernatural creature.
The romance was soft and fluffy with some mild teen angst, all based on the Soul Mate Principle - the idea that there's one perfect person for everyone and the books told the stories of people who found their soulmates. Humans and vampires, vampires and vampire hunters, shapeshifters and humans...Witches and humans... and so on. With some end of the world prophecy drama thrown in as well in the later books.
The last book in the series is still not out and I'm still waiting. This was another series that lead me to a wonderful on line fandom, where I joined fan clubs and made friends and found and started writing fan fiction and discovered RPG games and all sorts of fun things. So for that reason they still have a special place for me.
But there was something wonderfully addictive about them that makes me still love them.