Their care is pretty straightforward. Think of them as a small grouper. They reach about 5". Most of them seem to be active mimics of other fish - but only in the eyes of the crustaceans that they eat. So - a "shy hamlet" is actually a mimic of a rock beauty. A shrimp sees it through its eyes and can't tell the difference - but aquarists easily can. So , the model is diifcult for people to identify. Some of the hamlets are mimics of larger damselfish and the blue hamlet is a good mimic of the blue chromis.
At one time, they were are all considered the same species since the ONLY way to tell them apart is by color pattern. Taxonomists then decided to split them into a bunch of different species, but I've never been convinced that the differences in these fish is genetic and not environmental. In any event, expect a hamlet's coloration to fade greatly in captivity - that single point is probably what is making them "rare" in the trade as they certainly are not that rare on reefs.
Jay