OpenSolaris can be considered both a desktop Operating system and a very stable and capable server operating system specially for enterprise scale deployments where virtualization is required in different level along with SA and high availability which are inseparable parts of an enterprise.

There are few books available for OpenSoalris including Pro OpenSolaris and OpenSolaris Bible which one can choose between them. I was reading OpenSolaris bible and post a review in DZone which may helps other to get a better understanding of the book content and quality