I've just bought the "Ill Met in Lankhmar" by Fritz Leiber, but I don't know what to expect.

Have anyone read it? Can they tell me something about it? Not any too big spoiler please :)

Basically it is the story of the events that result in the formation of the partnership between Fafhrd (a barbarian/skald) and the Grey Mouser (a warrior/wizard/thief). There is an origin tale for each of them that details where each of the characters come from and why the left their respective homes and came to Lankhmar and then a story of how they met and had their first adventure together.

The stories are in the epic fantasy genre and are most comperable in feel to the older Conan stories. While the characters certainly fit the original meaning of the title hero they certainly do not meet the modern definition. They are not nice people - they are almost always primarily concerned with looking after themselves and they lie, cheat, steal, murder, get drunk, go wenching etc.

All the Fafhrd and Grey Mouser book are a lot of fun -- as long as your not very puritan about them. The book are some of the original references used by E. Gary Gygax in developing D&D -- you even see the influence in Baldur's Gate (the password given by the thief near the gates). The distinct advantage of Leiber's book over some more recent fantasy is his ability to not take his heroes too seriously.

Yup, this along with Conan are the classic adventure/brawler S&S. Get them all if you can. Thief and barbarian fans, this IS the gear.

They may be classic but they arent very good. I found them dull and uninteresting.

Yeah I would have to agree with joacqin on that score. I found them to be vastly overrated.

Among his many charming tricks Leiber, on several occassions, set the stage for an exciting adventure and then decided to skip past actually writing about the adventure.

When he decided to actually write about adventures there would be a long lead in and then the plot would just sort of resolve itself in an instance. The first book wasn't so bad at this but after that it got much worse - with one exception that I can think of.

There was also a tendency to have Fafhrd acting as an intellectual one minute and then a brain dead idiot the next minute in order to make the plot work.

I thought that they were quite good. The stories can be very creepy. Lieber is heavy on atmosphere, light on character development. The two anti-heroes are really just archetypes. They don't really change as people.
That said, I found the locations and encounters to be interesting and often chilling.

Thanks for your tips guys :)

Jst on thing, this is the first book right? So there's no other one I've overlooked that I should read first.

Yes, it is the first book.