[montsnmags]

Perhaps The Fionavar Tapestry, by Guy Gavriel Kay? It's a trilogy consisting of:

[Note: Spoilers at links]

• The Summer Tree
• The Wandering Fire
• The Darkest Road

To exerpt from the first link, "the Fionavar Tapestry is a trilogy of fantasy novels by Guy Gavriel Kay, set partly in our own contemporary world, but mostly in the fictional world of Fionavar. It is the story of five University of Toronto students, who are drawn into the 'first world of the Tapestry' by the mage Loren Silvercloak. Once there, each discovers his or her own role and destiny in the framework of an epic conflict". This sounds very simplistic, but Kay is a better writer than the Wikipedia summary.

Cheers,
Marc