Rooms is a family of modules that allow you to manage bookings primarily for the accommodation industry it is suitable for hotels, B&Bs, vacation rentals and agencies that manage multiple properties.
If you are looking to create a fully customized booking solution for scenarios such as the ones above from scratch install Rooms on a vanilla Drupal site with all its dependencies. You will be able to use standard Drupal techniques to customize further.
We have updated documetation on Rooms 1.9 and over here: General Documentation
If instead you are looking to get a head start checkout out roomify.us for access to our open-source ready made solutions for:
Vacation Rentals - Casa
Hotels and B&Bs - Locanda
Multiple Properties - Agency