ABANDONED. Fantasy - Boys go in search of a friend and they team up with Dionysus

[Joanne]

All i know is they enter this world after their girl-friend disappears, then they get a knife that is in a special pouch cause it cuts anything, then they meet dionysius who is having a party and travel with him to a demon city type place. It is NOT subtle knife and it has nothing to do with Percy Jackson.

[Lobstergirl, au gratin]

Joanne, are you still looking for this book?

[Sue]

This could be 'The Homeward Bounders' by Diana Wynne Jones. The knife is actually a girl's arm, which she can make into anything by concentrating. There is a place they visit where everybody is perpetually tipsy, from drinking something called 'creema de leema'.

[Tanner]

Sounds like 'Fear the Fantastic' (book 6 of the Everworld series by KA Applegate). 3 boys and a girl enter a parallel universe, the books are about their adventures while searching for their missing friend. They have a pocket knife made of special steel that cuts everything and in this book they join up with Dionysus and travel to the city of the main antagonist.

http://booklistreview.blogspot.co.uk/...

[Lobstergirl, au gratin]

No response from Joanne, moving to Abandoned.