A screenshot of Blackbox in its default configuration.
I used 0.65.0, which is the latest stable version. It dates from September 2002.
The man page is very good.
There are many themes. Basic window shape and buttons don't change, although there's a significant change to the appearance. Behaviour doesn't change with theme changes.
I'm not a fan of WindowMaker, and this is based on WindowMaker in spirit - the behaviour is certainly very similar. But the look is very different, the reliance on the dock/slit is less, and I much prefer Blackbox. Requiring a separate utility to make keymappings could be argued as a pro, but it seems like a significant drawback to me when the utility takes up more memory than the WM itself.
The most prominent feature on screen (if you're not using the slit, which is essentially a clone of the WindowMaker dock) is the toolbar. This tells you which workspace you're on (and if you haven't used Blackbox before, there's only one workspace until you create more), which window has the focus, and the time. It has two sets of left-right arrows: the set near the workspace name at the left end of the toolbar page through the workspaces, and the set at the right end of the toolbar cycle through the active windows. Retrieving iconized windows is a bit painful: you have to right-click on the desktop to get the main menu, select "Workspace List," select "Icons," and finally select the iconized window you want.
Like aewm, Blackbox has proven itself an extremely popular base for creating new window managers. It has spawned (and this is only my knowledge) Fluxbox, Hackedbox, Openbox, and Waimea ...
Utilitarian and nice to look at. Support for WindowMaker dock applets. Fairly small.
Separate keymapping utility uses a surprising amount of memory (~2 Mb).
The mailing list is still fairly active.