If you want a Surface Book case, your options are limited, but here are some worth considering

[Windows Central]

If you want some added protection for your expensive Surface Book, sadly it's slim pickings out there.
Most laptops don't exactly lend themselves to cases, but the Surface Book also isn't most laptops. For one, the entire display portion detaches from the keyboard so you can use it as a tablet.
So, with this added versatility you might want to keep it a little safer than any 'normal' laptop. You can get a case, but sadly, there's not much to choose from.
There are a few in particular that stand out as worth a look.

Full story from the WindowsCentral blog...