What it says on the tin: MM-style NPC stat blocks for a variety of archetypes, mostly drawn from PC classes. Nice presentation, has some unique mechanics and weapons (like the City Watch's Mancatcher weapons) listed for certain variants. If you like and use the MM NPCs more than PHB NPCs, you will enjoy and appreciate this book. Even if you prefer to create NPCs using PHB methods, you will still derive some value from the spell lists and fluff text, and from NPCs like the Smith, the Ruler, and the Street Urchin who don't come from PC archetypes.
I'm giving it four stars out of five because I felt the product is a bit shallow, on par with the 5E MM but not exceeding it. In order to get five stars the product would need to supply insights into how to use these NPCs effectively at a glance--after all, stat blocks are the easy part. Coming up with motivations and behavior is hard.
For example, I'd love it if a given archetype (Necromancer) had a short list of common Names (Theophilus the Grave, Uric of Tibia, Sazael); common Motivations to create potential conflict with the PCs (Plunder treasure, Steal Bodies to Animate, Trade/Steal Spells); common Tactics in a fight (order zombies to attack and cast Stinking Cloud followed by successive Fire Bolts; as soon as the tide turns and six zombies are defeated, Dimension Door away and Hide); and common rewards for allying with/pleasing/impressing/defeating them (Bounty: 500 sp from local sheriff for killing known criminal; a collection of skulls with gems inset for eyes totalling 440 gp in value; a lengthy lecture detailing common weaknesses of ghouls, vampires, and liches, and how to spot the signs of their presence; membership in a secret cabal).
