Pros and Cons of Lamentations of the Flame Princess. Additionally: How to Prep, and the Game's Basic Tenets As I Know It, After 4 Year's Experience

THE PROS OF A GAME OF LAMENTATIONS OF THE FLAME PRINCESS:

1. The game simply enables quick, deadly, and meaningful combat. This was the retroclone that did it for me and keeps on doing it.
2. Character creation is brief.
3. The rulebook is lightweight, full of good art, and generally easy to reference.
4. The skill system is versatile and lightweight and simple. It also encourages "avoiding the roll": the player is encouraged to use inventive techniques to avoid the often difficult skill checks.
5. "Avoiding the roll" is innate to the tactics. The stats are imposing, and this encourages imagination over rote gameplay. 
6. The GM does not know how the PCs can win or even if they will win, so the story is that much more uncontrolled and up to the player's wits.
7. Diplomacy is not a roll, instead it's up to the referee's rulings. In my games the players have to offer good reasons for NPCs to do what they want.
8. Heavily balancing the odds against the players means there's no reason to flinch when the PCs acquire some kind of heavily overpowered item/spell/demon. 
9. The game's portrait of magic is "high risk, high price, high reward" which makes for good horror storytelling.
10. The rulebook has many hidden power levers, the Summon spell is the most standout.
11. A focus on horror is a focus on glorious and weird adult drama.

THE CONS:

1. Players should be warned/informed of a number of factors:
1. Player Characters can easily die.
2. Extreme content. You need to ask what everyone's comfortable with.
3. The skill system is radically different than D&D's. Ditto for magic, XP, leveling up, classes/race, and diplomacy.
4. Combat is super deadly, retreat is important to keep in mind.
5. There are special combat options (charge does double dmg, press, parry, etc.)
6. Alignments don't govern behavior.
2. Being able to improvise well requires having a proper prep workflow (see section below).
3. The encumbrance system works best if it's not thoroughly addressed.
4. Fleeing from combat is somewhat under-written.*
5. Rules for stealth, sneak attack, helplessness, and surprise are not collated.
6. The system of saves is a pain to copy down or check against and seems overcomplicated.
7. The skill system is often confusing for new players.
8. High player character death volume can be demoralizing and hard to explain in the fiction.

"Young Girl Eating a Bird" Rene Magritte,1927

How to prep for LOTFP well:

• Make a large map which has loosely sketched locations on it.
• Have a handful of modules or adventure locations which you bought, read, or wrote, and have (agonizingly) sat on for years. Put some of these on the map.
• If the PCs go beyond your prep, you need to be able to improvise until the end of the session, and then spend the interim week catching up. This is the core of the workflow-- bringing something to the table, and if necessary, catching up between weeks.
• Be able to, at a moment's whim, discard hours worth of prep. This is crucial! if the PCs leave your adventure zone, you need to be able to keep up! Don't dawdle!
• As a gm, your role is imagining and writing stuff which may not ever be played, and the more gleefully you can embrace that, the more efficiently you'll prep, and the more fun you'll have. Plus you can and should save unplayed prep for later campaigns, even for years later in your life.

Basic Core Tenets of Lotfp (as I know it):

1. Success in adventure is not guaranteed.
2. Moral behavior is not especially rewarded.
3. If the players depart from the extent of the referee's prepared notes, the referee must improvise and follow their lead.
4. Humans and their power structures are usually predictable and genuinely powerful in their own rights. 
5. Monsters and magic are by nature horrifying, weird, and variously powerful.
6. If a participant in the game is not content with how the game is played they should address the group's agreements on how the game is played. 

The end result should be a game about planning and taking risks against desperate and weird circumstances, with unexpected results. It should spit out weird horror and invite unique contemplation. 

* It comes down to a fairly random roll off (1d20 + speed/10) with a few additions-- monsters have to pass a morale check if you drop food or treasure. Rules on how failed escapes work would be appreciated-- are the players are able to flee again after being caught?