UNIX for Advanced & Expert Users

hi guys,
I am system adminstrator in a company but now i want to shift to linux\unix platform in network and security line so could anyone help me out what i should first read which os of unix is running currently by most corporates and hooooow i start?

it really depends on how much your company wants to pay for stuff ... the software support costs need to be included in the evaluation of the os aside from the licensing costs ... and there's the costs for acquiring new hardware as well as supporting them ...

based on my travels only, here is what i've seen ...

financial companies tend to lean towards solaris
health care companies tend to lean toward hp-ux
retail companies tend to lean towards aix
web and software companies tend to lean towards linux
educational institutions tend to lean toward solaris before but a lot are leaning towards linux now

however there really is no 1 perfect unix ... you have to go with what you can afford based on your needs and your ability to support the new os ...

to start ... ask for quotes from the different os vendors and look at literature on the web ... compare features that you require and also look at how much flexibility the prospective new os will give you with regards to expansion, migration of apps, etc. ... and look at hardware costs as well as support plans ... browse the bookstores and/or libraries and scan the books to see if there is 1 os you think you can much more easily support over the other ...