What, any genre?
Personally I'm into more sci-fi and fantasy, so there's going to be something of a bias in my list here:
I've just finished reading the Mistborn trilogy by Brandon Sanderson. It's an epic tale of adventure, the overthrow of an evil empire, and a curious and detailed magical system called allomancy in which swallowing and "burning" different metals grants certain people the ability to do all sorts of cool Jedi stuff.
It's cheeky enough of me to slip a trilogy (which is itself part of a nonology, I hear), so I can't very much recommend everything ever written by Terry Pratchett in his Discworld series. However, I do recommend them very highly, particularly Mort and, oh, anything with the Sam Vimes character.
And then there's The Eyre Affair by Jasper Fforde. I literally cannot describe this one. It is pure brilliant mad genius that you just have to read. Go buy a copy. Now. And then all of the rest of the series. :P
That's three and I'm still stuck in the realm of fantasy, and I've actually given you way more than five books.
You could have a look at Rivers of London, a police procedural set in modern-day London. Oh, and the lead character is a wizard's apprentice and the suspect appears to be a two hundred year old ghost, manipulating people into playing out a sick play. It's interesting because it sorta shows the often horrifying effect of magic in a mundane world, while at the same time being really slick and funny.
Lastly, for a change of pace, you could try out Neuromancer, by William Gibson. It's a bit tougher, a lot less compulsive reading than my other choices. In fact I tried reading it once before and stopped a few chapters in. I was reading it wrong, though, expecting a techno-hacky romp thing. It's more of... it's jazz, only in prose. It's slow, moody and sets little tableaux of emotion and memory more than any action. At least, so far it does. It also happens to be a cult classic and a book which pretty much defined the term cyberpunk, so it's pretty much going to turn up on the reading list of anyone who liked, for instance, Ghost in the Shell or Deus Ex.
Anything and everything by Neil Gaiman - I particularly liked Neverwhere.
Patrick O'Brien's legendary Aubrey/Maturin series, about the fortunes of Captain Aubrey during the Napoleonic Wars (You may remember the film, Master and Commander).
Philip Pullman - I like the His Dark Materials trilogy, but better still is his book The Good Man Jesus and the Scoundrel Christ, putting his own narrative stamp on the events of the New Testament.
The Algebraist, by Iain Banks. A cast of truly imaginative aliens, a universe in which space travel takes a really, really long time, and thus distorts human lifespans to extreme degrees, and the hunt for the only technology to save a world from a malignant force.
The Sherlock Holmes novels: Not only are they fun stories, it's interesting to see the lax attitude to Holmes' cocaine habit, the casual racism, and Holmes' bizarre use of phrenology in his deductive reasoning.
The Jason Bourne books. Like so many other books, very different to the films, so worth a read if you liked the films but think you know the plot: You don't. :P
I haven't paid attention to your 15 year stipulation because a good book doesn't have to be a new book, and also I have no idea when these were published. Some are within, others are bound to be older. I've erred away from period stuff like Jane Eyre, though, so hopefully you won't mind too much :)