From the publisher's website:
"GURPS Infinite Worlds describes Infinity Unlimited, a mega-corporation that uses high technology to cross between parallel worlds."
"But what if the world-jumpers were not technicians, but wizards? What if Janus himself, the god of doorways, shared the spells and rituals needed to break through the quantum walls? The answer: Collegio Januari. It's a powerful guild of wizards, piercing the veil between their world and others, searching for knowledge, wealth . . . and mana."
"Written by Kenneth Hite, this campaign setting brings world-hopping to the traditional fantasy genre. It can be dropped into either a GURPS Infinite Worlds or GURPS Fantasy campaign, and can be easily adapted to any low-tech game featuring wizards and knights."