Yes, this book contains material that was in Street Magic but that did not make it into Street Grimoire. Does that make Street Grimoire incomplete with a nefarious plot to sell you back lost content using this supplement? Probably not.
Shadow Spells throws in more magical traditions, some of which have been tweaked in drain code formula from their previous appearance, more magical societies with their membership and stat blocks (!) of their leadership, threats to Awakened individuals, and new spells, ritual magic, and adept powers. This particular supplement feels more like designed for GMs, considering most of the powers have a pretty nasty bent to them. However, there are some nice adept powers in here and the costs are far more in-line with what's present in the SR5 core book. And yes, there are adept powers here that were referenced in Street Grimoire but had not been included in the first print. HOWEVER, the errata for Street Grimoire also includes those missing powers.
There's a couple typos here and there and words that should not be, and a weird reagant cost table floating around at the very end that applies to nothing in this book. I wish there was an index though there is only 24 pages to flip through. But overall, I was pretty pleased with this supplement. It's very straightforward. Not exactly groundbreaking, but I did really enjoy the potential adventure hooks presented here.
[4 of 5 Stars!]