Information Technology Infrastructure Library

The IT Infrastructure Library originated as a collection of books each covering a specific practice within IT Service Management. After the initial publication, the number of books quickly grew within ITIL v1 to over 30 volumes. In order to make ITIL more accessible (and affordable) to those wishing to explore it, one of the aims of ITIL v2 was to consolidate the publications into logical 'sets' that grouped related process guidelines into the different aspects of IT management, applications and services.

While the Service Management sets (Service Support and Service Delivery) are by far the most widely used, circulated and understood of ITIL publications, ITIL provides a more comprehensive set of practices as a whole. Proponents believe that using the broader library provides a comprehensive set of guidance to link the technical implementation, operations guidelines and requirements with the strategic management, operations management and financial management of a modern business.

The eight ITIL version 2 books and their disciplines are:
The IT Service Management sets
1. Service Delivery
2. Service Support

Other operational guidance
3. ICT Infrastructure Management
4. Security Management
5. The Business Perspective
6. Application Management
7. Software Asset Management

To assist with the implementation of ITIL practices a further book was published providing guidance on implementation (mainly of Service Management):
8. Planning to Implement Service Management

And this has more recently been supplemented with guidelines for smaller IT units, not included in the original eight publications:
9. ITIL Small-Scale Implementation

Source: wikipedia.org