Books that you carry around with you for weeks just rereading them, books you tell your mates about (and then if you see someone reading the book you rush up and start a conversation with them because you know they won't mind) - books that, when you meet a person and find out that this person has read and liked that book you know you will be friends.
Ok here are some of mine
Robert Heinlein: Time Enough For Love Easton/Lizt: The Ethical Slut Paul Breeze While My Guitar Gently Weeps ANy Christopher Brookmyre (OK that is a bit of a cop out as so many people have read him) Gwyneth Jones Bold as Love series.
And if this thread gets more than one recommendation for Jodi Picault (interesting concepts, godawful writer) The Road Less Travelled, the Da Vinci Code or John Farking Grey's Mars & Venus (and you are talking aout of Uranus mate) I will.. Dunno. Pout, stomp and sneear at you all.
<flippancy on> OOh, the Da Vinci Code changed my world view . I became at least 150% more depressed about the state of the publishing market and the general level of intelligence in the world since something that bad could sell that many copies.
(Yes I have actually read it and am not basing my opinion on media reports) </flippancy off>