This sourcebook is mislabeled. Sure there are new monsters—various types of undead, creatures from the miniatures game and at least one new template (Lloth Touched). However, the reader may be confused when stumbling across entries for gnolls, ogres, etc. (“race” monsters). The opening paragraph on these entries states the creature has been covered before in MM but here are some more details and several pre-made NPC versions with class levels. For a DM, a pre-made gnoll ranger, orc barbarian or drow wizard does save some time yet this should be reserved for another book. Traditionally the MM books are for showcasing the core (or foundation) version of the monster, without class levels, unless it’s a “race” monster that starts with only one hit die, then the default is a 1st level warrior. Besides being a waste of space, there are also pre-made NPC versions with classes from the supplemental Complete sourcebooks: a gnoll warlock and a drow ninja. This may upset some people who either lack these materials or irk players who don’t have those classes in their campaign (again, it equates to wasted space).
Ever since DMG II appeared last summer, all adventures and Dungeon NPC listings switched over to the new format with everything the opponent could do in combat. It’s complete yet cumbersome and gobbles up more pages. It does save me some work on the tactics of the villain(s) or when I transcribe the stats to my monster/initiative cards. With MM IV I don’t find this format helpful when it comes to explaining a monster’s stat breakdown. The past format from MM 3.5 edition did it better.
Another bone of contention critics will classify as padding in MM IV will be the maps and pre-made encounters. Maps in a MM sourcebook on monsters? There is precedent in other sourcebooks such as various temples in Complete Divine and all Forgotten Realms material. The maps and encounters do dovetail nicely with the pre-made NPCs. It saves time for the DM should the players need a wandering monster encounter for XP, it’s a short night, the DM’s pressed (frequent situation for me) or there’s a rut in the campaign. Again, I don’t feel this belongs in a MM, it should be reserved for Dungeon and encounter books filled with short adventures.
Bottom Line: Of all the MM books in this series, MM IV is the most disappointing and least useful. If you don’t own the other source materials, the templates for the gnolls, drow and orcs won’t do you much good. If you don’t plan on running a campaign with Tiamat’s followers being rather prominent, most of these monsters are pointless. With those two disqalifiers being pretty strong supplemented with the less helpful format and strings of encounters, IV is only for completists, map fanatics or people with $35 to blow.