Right now, this is an absolutely essential book to playing the Strange. The corebook, while it features some very creative options, is very limited. Some Foci are tied to specific recursions and you wind up feeling like people are stepping on one another's toes if you are using only the core Foci.
Ryan Chaddock's Translation Codex meanwhile provides a couple of great ideas for recursions, but the real win here is the huge number of Foci for five different flavors of settings: High Fantasy, Low Fantasy, Modern, Science Fiction, Psionics and a number of smaller categories including Westerns and Myths. This is almost essential for folks to put together a really in-depth group and make the characters they really want to.
My only complaint (and it's a small one) is the new Foci don't include starting equipment. The corebook Foci do, so if players are mixing between the Corebook and the Translation Codex, they can get a little muddied on who starts with what. Other than that tiny quibble, this book 100% meets everything I was hoping for.
Final thoughts: If you're either a player or a GM and playing the Strange, snag this. It's worth every penny.
[5 of 5 Stars!]