There's a good bit of design documentation here: http://www.ravenbrook.com/project/mps/master/design/

And hopefully this will change forms in the coming months to something more modern / up to date.

There's also some stuff here: http://www.ravenbrook.com/project/mps/master/manual/wiki/

MPS allows for precise rather than conservative GC. It supports doing copying collectors (see poolamc in the design docs for example).

It has some pretty nice telemetry and event logging as well.

Overall, I really like MPS and it is pretty powerful. It is a nicely structured library. It is more work to use than Boehm, but it does more than Boehm.