In the past I have always chosen to compile my own PostGIS because the GEOS library that came with the regular PostgreSQL yum install, was a bit antiquated.
This has changed, so this time around I figured I'd give it a go at using the Yum repository 1.5.2 release of PostGIS available via Yum Package List.
Before you can follow these directions, make sure you have your PostgreSQL 9.0 setup via our An almost idiot's guide to Install PostgreSQL 9.0 with Yum.
PostGIS in Action has started shipping from Amazon and we already have 3 positive reviews. We are hoping to write another book sometime soon, but haven't decided yet on the topic. Will definitely have something to do with databases and probably a lot of PostgreSQL in it.