<p>What's the widest overview and where are the deepest analysis of different replication methods and problems?</p>

In my opinion, you should pick a mainstream database (such as Oracle) and study everything it offers and go from there.
Oracle offers:
Replication
Data guard (standby database and beyond- physical, logical)
Real Application Clusters - (multiple instances, one DB)
and more !
A bit of hands-on would not hurt so you can download a PC version and try various replication approaches on one PC!
Enjoy !