These very well may be books that are popular, depending on your reading habits. But I am aware that they are not "popular fiction" or at least I'm not aware that my friends read them, as I persuade them to buy them all!
Thus, they are split into two categories and I've limited the number of books I can ramble on about!
Newer books that you probably already know about:
You Don't Know Me by Sophia Bennett - a beautiful and quite popular book about friendship and peer pressure.
Velveteen by Daniel Marks - very gothic and funny tale about ghost hunters in purgatory but very American so not so well known over here.
Night Huntress series by Jeaniene Frost - another American writer, a very big vampire series with mixes of romance and thriller but not many of my friends have heard of them, let alone read them!
The Working Stiff by Rachel Caine - start of the Revivalist series, full of dark humour and gruesome details. The lesser known of her novels, I feel, but still very good.
The Name On Your Wrist by Helen Hiorns - the winner of Sony Young Movellist Award, a brilliantly written commentary on free will and the price of love.
Older books that I fear have been forgotten:
Cat Royal series by Julia Golding - I loved this series growing up and it is the reason I love history and historical fiction. It's a great introduction for younger readers to a dramatic period of history.
Lost Souls by Poppy Z Brite - a set text for uni that I read last year, very gothic and dark but funny, if a bit weird. Only for readers of a certain taste.
Dan Leno and The Limehouse Golem by Peter Ackroyd - another book for uni, one I really enjoyed and left me a little breathless from its twist ending.
Dear Dylan by Siobhan Curham - her first novel and the book that introduced me to her superb writing style, not to mention my first review book! Tells of a teenage girl who emails her hero and finds a friend.
The Mediator series by Meg Cabot - less known than her bigger series The Princess Diaries, a series of 6 books about a teen girl who can see ghosts and attempts to help them move on. One of the first paranormal books I read and almost certainly the reason I fell in love with the genre.
Are there any books you'd like more people to read, fear that they've been forgotten? Agree with what I've listed or think I've missed an obvious one?