An interesting introduction to The Strange universe. Enough diverse challenges to suit most groups and play-styles. Offers up travel to enough different Recursions without overwhelming the players. The antagonists and other NPCs are intriguing and well-developed. If I do have one complaint about this supplement, it is the final act - which takes players to an area best saved for End Game in a Strange campaign. This one section reveals the most significant secret in the Strange universe, and doesn't handle it with the reverence it deserves. As a GM, I'd definitely alter that section.
Otherwise, a solid addition to your collection.