Did anyone ever doubt that this would find it's way onto the list? I'm not one to definitively say what my favourite book of all time is, but if really pushed I'd say The Lies of Locke Lamora. There's just something about the book that hits me where I live every single damn time I read it.
I recently participated in a thread on Fantasy-Faction where readers were asked to name one of their favourite lines from a book and one of mine comes from The Lies of Locke Lamora. It's the opening sentence and the book had me hooked from that one line. I picked it up one lunch time after succumbing to the hype around it, and read the start on the tram on the way back to work and I was enthralled. It actually really sucked that I had to work that afternoon, because I could have quite happily jumped on the train and gone home reading the book.
I recently reread it (I think that was read number 16), and it honestly gets better with each subsequent read. It's not flawless, nothing is. There are occasional holes in the plot and some of the interludes are unnecessary, I personally like them, but I can see someone making the point that a couple could have been cut, although I think they add to the sense of reality that the setting (the city of Camorr) had. Camorr was like this extra character in The Lies of Locke Lamora, and while the sequels (Red Seas Under Red Skies and The Republic of Thieves) have been excellent books, they lack a little something for me. There are a few factors, but the absence of my old friend Camorr is definitely one of them for me.
It's about as close to a perfect work of fiction that I can ever remember reading, and after 16 reads I'm still not sick of it, despite being able to quote slabs to near word perfection when I do read it.