Just in case that didn't satisfy you, the Trainz Wikipedia and Trainz Wikibook are also out there to peruse. Speaking as a long time contributor to both Wikipedia and Wikibooks, the Trainz wiki linked in the tabs above needs volunteers (and generally should be considered in intensive care, seems to be a good idea that never got off the ground).
http://en.wikibooks.org/wiki/Trainz
http://en.wikibooks.org/wiki/Trainz/Things_You_Can_Do_In_Trainz
http://en.wikipedia.org/wiki/Trainz
If bottom line budgeting is an issue, buy a cheap used (probably non-registrable) copy of TRS2004 or TRS2006 and give it a spin, but given the sales pricing to download newer ones, it's a no-brainer bargain to get the last version your computer will run satisfactorily... they demand more processor/graphics the younger the release. See my bio page for how TRS2006 has happily filled up four years of my time! Bargain prices for entertainment considered against say a half-dozen DVDs or paperbacks you'd go through in a few days steady use... Trainz won't let you get bored, if you've an imagination.