Expert's answer

At the official ITIL Web site, you can find overview information, links to order the ITIL publications and links to the ITIL knowledge center and information about how to earn credits towards ITIL qualification and ITIL certificates. Version 3 of the ITIL was published in May 2007 and is an evolution of the standards and practices embodied in ITIL Version 2.

There are five core volumes in the Official ITIL Lifecycle Publication Suite, which is available for purchase from a number of vendors, including this one.
You can find general information about Versions 2 and 3 of ITIL and links to additional resources on Wikipedia or by searching on ITIL in a search engine. ITIL is a framework of best practice guidance for information technology service management and like other best practice frameworks needs to be viewed through the lens of your own organization and requirements. As ITIL adoption continues to spread, becoming familiar with the concepts and vocabulary can enable more productive discourse with others grounded in the same terminology. ITIL claims to not be prescriptive about implementation details or to have all the answers, but rather provides guidance and structure for integrating and expanding best practices in the organization’s information technology service delivery and management. There are forums dedicated to ITIL discussions, here and here.

Another resource I would add is the ITIL FAQ. One of the most important statements in the FAQ is that "ITIL books emphasise that organisations that have succeeded in implementing ITIL have one important thing in common - a strong 'Executive Sponsor'." While this is true of most successful large IT projects it is especially true of documentation/standards implementation projects that change working practice and accountability mechanisms. If you are confident that the opportunity in front of you includes solid high level sponsorship then start digging in to the material keeping in mind that the rules are more like guidelines and begin engaging your team members to develop a shared understanding of the ITIL vocabulary and use it to identify the portions of the ITIL core processes that you will begin with. You can establish yourself as the ITIL lead along the way to becoming a true ITIL expert. I think you will find that much of the material codifies many things you and your team already know about best practices.