It's an excellent lens to take with a grain of salt, meaning it's a microscope more than a lens.
You cannot do the portraiture of your wife with this lens, and it's where is the grain of salt, in fact if you plan to buy this lens you should know that you will do only macro, landscape, portrait or whatever it's just impossible !
1 to 2 magnification is okey .. over 3 you do need lights to see somethings in the viewfinder !
Very dedicated lens, you will do your macro/micro with an excellent image quality! may be one of the the best IQ that Canon lens produce.
No focusing system at all ! not even a manual focus ring !
It's a manual lens where it's a fixed focus (move the chariot you use or your body backward/forward to focus).
Aperture f/16 Max at the smallest aperture give you a very short DoF at those magnifications, so f/16 it's still very very short DoF here.
Use : mostly for dead insect > you can't get near enough with alive insect without scare them, ants it's ok, you can, but flying alive insect i gave up.
I use it also for focus stacking, water drop on plants, pistils, etc ...