What makes a supplement not very useful

Generally speaking, what makes a D&D supplement not very useful is when it is too vague.  This vagueness comes in a lack of detail or an amount of detail that leaves the player or DM saying: "I could have made that up, why did I spend my money on this"

If good and useful supplements deliver (1) adventure ideas (2) roleplaying ideas (3) new rules (4) get your imagination going

Not so useful supplements are missing some or all of these elements.

Another dimension of usefulness is how specialized the supplement is.  Obviously if you always play rogue characters, a book about paladins will be less useful.  Similarly if the campaign involves mostly standard dungeon crawls and the supplement is about a place lacking in dungeons to crawl in, that supplement will also be less useful.  In this regard, the gazetteers are mixed.  The following are fairly conventional and will accommodate a standard adventuring party with little difficulty:

Karameikos, Ierendi, Northern Reaches, Minrothrad, Darokin

The following are written for culture or race specific adventuring but can still accommodate outsiders who are visiting fairly easily:

Ylaruam, Alfheim, Rockhome, Five Shires

The following are written for culture or race specific adventuring and some or all members of a standard party will run into difficulty:

Glantri, Thar, Ethengar, Shadow Elves, Atruaghin

The biggest problem that hurts a supplement (any edition) is vagueness.  The language fills up space but does not really convey any information.

Most useful information found in Mystara/Known D&D World Gazetteers

The most useful information that is found in some but not all gazetteers are the following:
 
1.  Adventure ideas
2.  Campaign ideas
3.  Interesting character variations
4.  Workable background information
5.  Politics and Rivalries

Adventure ideas:  Many DMs can come up with fairly good adventure ideas on his or her own.  When purchasing a product like a gazetteer most DMs are interested in time-saving opportunities.  Solid adventure ideas with a workable framework are very useful.  These adventures should also be distinct as to setting.  Adventures that are too generic are not as good.

Campaign ideas:  Similarly ideas for how a gazetteer can be used for an extended series of adventures is very useful.  It saves time and makes it easier to build a storyline.  Again these campaigns should be distinct to the particular gazetteer.  A campaign in "The Five Shires" should be different than one in "The Emirates of Ylaruam".

Interesting Character Variations:  Optional rules for the players are almost always interesting.  This most often is variations on character classes or new abilities or new spells.

Workable background information:  Background information about the economy, history, and culture (etc) of the gazetteer should be broad enough to allow some tinkering.  It should not be too broad so as to be too generic.  In other words there should be good "out-of-the-box" functionality but it also should be options for "customization".

Politics and Rivalries:  Well-done political intrigue always makes for better reading.  Good politics and rivalries also make for interesting adventures as the characters work with or against various factions.

The best gazetteers offer adventures and campaigns based on both political intrigue and interesting locations within the gazetteer.

Ranking the Gazetteers of the Known D&D world (Mystara)

The Known D&D world (later named Mystara) is made up of a bunch of countries that were defined in 1981 in the module X1- Isle of Dread.  Each country was given a short description.  Starting in 1987, a group of publications called Gazetteers were produced based on the short description of each country.  Each Gazetteer detailed one country on the map.  The Gazetteers are between 64 and 96 pages long (each).  They provide an overview of the history, culture, geography, and special rules for each country.  They are not fully compatible with each other in that there are contradictions and continuity errors that are unresolved.  (Nothing major).  Often but not always the continuity errors relate to descriptions of Gazetteers yet-to-be-published at the time of writing.  The Gazetteers were outsourced to freelance writers although the person responsible for hiring freelance writers (Bruce Heard) wrote two of the Gazetteers (Thar and Glantri).

Ranking the Gazetteers from best to worst:

Great: Interesting Setting, Good adventure ideas, Good Execution (of ideas), Fun, Makes you want to go there

Good: 4 out of 5 of the above traits

Ok: 3 out of 5

Poor: 2 out 5

Awful: 1 out of 5

Or- Has a negative trait (or two) that cancels a positive trait

Negative traits:  Too much fluff-empty banal text that adds nothing; Weak on rules; Logical error(s)-it is fantasy but some of the rationale for why/how is suspect; Tries to accommodate all races and classes when this doesn't make sense based on the setting-Minrothad Guilds is the most flagrant violator; "My gazetteer is indestructible syndrome"-the better ones clearly aren't indestructible; too much blank canvas- too much detail in a particular area is left for the DM which somewhat defeats the purpose of buying a gazetteer in the first place.

 

GREAT

Principalities of Glantri (Gaz. 3)

Orcs of Thar (Gaz. 10)

Golden Khan of Ethengar (Gaz. 12)

Elves of Alfheim (Gaz. 5)

 

GOOD

Kingdom of Ierendi (Gaz. 4)

Dwarves of Rockhome (Gaz. 6)

Grand Duchy of Karameikos (Gaz. 1)

Northern Reaches (Gaz. 7)

Hollow World Boxed Set (an Edgar Rice Burroughs type of land underneath Mystara)

Voyage of the Princess Ark boxed set (based on the Dragon Magazine column of the same name- details an India-like setting, a sub-Saharan Africa type setting, and rules for similar ships)

 

OK

Shadow Elves (Gaz. 13)

Dawn of the Empires (Boxed Set about Thyatis and Alphatia)

Emirates of Ylaruam (Gaz. 2)

Top Ballista (Silly rules for gnomish flying city complete with magical WW1-style aircraft

Tall Tales of the Wee Folk (The Faerie Kingdom near Alfheim with rules for playing pixies and sprites, etc)

The Sea People (Rules for playing undersea characters)

Night Howlers (A valley full of werewolves)

Five Shires (Gaz. 8)

 

POOR

Minrothad Guilds (Gaz. 9)

 

AWFUL

Atruaghin Clans (Gaz. 14)

Republic of Darokin (Gaz. 11)

Note: I intend to Review each of the Gazetteers on this blog.