I found an excellent post on CQRS (Command Query Responsibility Segregation) by Rick van der Arend. A Dutch version is available too: CQRS & de bijkomende architectuur. This post not only introduces the principles of CQRS, but motivates them too, e.g. it is argued that the introduction of event sourcing offers a solution to keep your domain model clean of getters and setters and makes it possible to restore state without performance problems. This is exactly what we found out implementing our current application for booking office rooms (we first tried to go without event sourcing)!
The pictures that are used in the post are also very instructive: