Full disclosure: I am friends with Jess Hartley, the author of this supplement.
This is the first Instant Antagonist supplement from Flames Rising Press. It is intended to be used in any modern supernatural/horror game.
There's a brief introduction to what the IA line is about, then a one and a half page story about (one version of?) the succubus.
The next few pages are a physical and social description of the succubus and how she interacts with typical situations. There's an interesting but short summary of her "mind, body and spirit" which is meant to be used to translate her into the systems of your chosen game.
The supplement concludes with three possible origins for the succubus as well as several story hooks.
The strength of the supplement is the detailed examination of how the character interacts with people and situations. However, the main weakness of the supplement is that there isn't enough of this examination.
For example, the character's behavior at parties and in intimate situations is thoroughly worked out. This is exceptionally good fodder for a GM. I have a clear picture after reading this how this character will be if the characters encounter her in those situations - something very few character supplements bother to do. But I don't have a clear picture of how she would react if seriously threatened, unsettled or if there was an obstacle in her way, for example, or what she actually does with "her" time. I feel like I can get the player characters to bite down on the hook but have really no place to land them. Nevertheless it's both unusual and really helpful to have a "social description" of the antagonist, since the characters are likely to encounter them in a social situation at some point and normally GMs are left just twisting in the wind with a very generalized "personality" block.
Another big strength of the supplement is that the different origins discuss the different sorts of relationships and connections the player characters can be expected to feel with the antagonist. For example, if she is the "devil's daughter", she really has no control over her parentage and, as the supplement notes, the PCs may be sympathetic to her situation. On the other hand, if she gained her devilish powers through pacts with hell, the PCs may rightly condemn her. This is often not discussed in monster/antagonist materials - how is the origin and activities of the antagonist likely to contribute to the player characters' attitude towards them? The same is true for different player characters. If I'm running a game of crosses-and-stakes demon hunters, they are likely to have a different attitude towards Lily than a group of vampires who are themselves cursed to seduce and consume humans. They are also likely to react differently to her depending on the "rules" of the world as far as magic, demons and so on go. This is well fleshed out in the origin section.
The story hooks are quite good, but they end up with too many questions without much guidance in how I should answer them as a GM. It's a good thing when you're providing adventure hooks to make them very broad so that they can be fit into different sorts of campaigns and groups - but there also needs to be enough to them that I can figure out whether I want to fit them in, and how I decide that.
If I had to sum up this supplement (and I guess I do or else the review will go on longer than it does), I would say that it's got a lot of really awesome stuff in it that leaves you hungry for more. I hope the IA line is successful, it's an excellent idea - antagonists can really drive your story. Lily the succubus is a cool, iconic character who could turn up in any number of games that I've run over the last few years and certainly she is likely to turn up in one in the future, and that's the best recommendation I can give her.