Please note that the review is sorted from negative to positive. So, please do read it till the end where the good stuff comes.
The most significant weakness of the book lies in the lack of actual play examples. Together with the overviews missing some details (like the roles moving to the left after each scene), this makes visualizing game play and checking on the rules sometimes difficult. Mind you, generally, the rules are clear and usable as written, but sometimes obscured by those design decisions.
Some things are actually not really explained, for instance the list of locations you generate in the beginning - is that an exclusive list, should you try to include all of them, or what other impact do they have on the game? I had to ask for support there and was informed that it was not an exclusive list.
While some may argue that the following is the biggest problem of the book, after analyzing it, I have come to the conclusion that it is not as bad as it feels. Lovecraftesque discusses two problematic issues found both in Lovecraft and his writing as well as in many derivative works, including RPGs. These are racism and distorted depictions of mental illness. There are quite interesting articles on them in the book, which I consider useful. However, that useful look behind the curtains (which even includes some thoughts on real life PTSD) is overshadowed by a preaching tone. In addition, when the book discusses the hopefully standard discussion before playing a horror rpg of what things are to be avoided because players feel uncomfortable with them, the authors seemingly belief that allegorical racism and comic depictions of mental illness are the main issues people may have. Personally, I find it much more import to check if anyone has arachnophobia or something similar, as the game is meant to provide detailed descriptions, which could easily make people with the appropriate phobias feel uncomfortable or even get a panic attack, rather than delve into academic fields like allegorical racism. Combined with the rather unfortunate "should" instead of "may" in the sentence introducing the examples of items to be banned, we get that unfortunate impressing of heavy-handed preaching. On a personal note, if you wish to avoid allegorical racism, I am not sure you are well-adviced to play a game that features alien creatures/monsters, as they can always be seen as allegories for other races or groups of people.
Another item that some people may have a problem with are a few pieces of poetry in the vein of Lovecraft's own poems. Some people may find them a waste of space, while others may find them useful to get into the mood. In either case, it is a noteworthy and unusual design decision.
One very good thing about this product was customer support. I mentioned above that I had a rules question. I went to the homepage to see if I found some clarification there, and as that turned up no result, I used their contact form to ask the question. I received an answer within 24h and got the impression that they cared about their customers.
The core rules are rather versatile, the game is statless, allowing players to change the premises of the game. If you stay within a framework of horror or mystery, you will probably not need to do much beyond agreeing upon such a story. Otherwise, you may need to alter the rules for Creeping Horror or the Force Majeure. The one element that is rather inflexible are the special cards - each player gets one card and by playing the card, an element can be introduced into the game that would usually violate the rules for the (early) game. The elements that are added by the special cards are focused on supernatural horror; while some can still be used more generally, others may be a bit more difficult to port. Still, that is not an insurmountable hurdle, so I could imagine even warping the rules so far to do a classic tale of dragon slaying.
As I said above, the game is statless. The main character, called Witness, has traits that describe their personality and gains them through play, but they have no mechanical meaning instead being a guide to keeping the character consistent. Conflicts and challenges are judgment calls for the current game master, called Narrator, and much is based on the phase of the game (3 phases with fixed number of scenes (with some variations in the second phase)). This means that the game does not come to a halt when a stat is needed or statistics for a roll are calculated. The game is diceless and has no randomizers besides the special cards which are introduced at the whim of the player that holds them. It is an unusual approach, but one that clearly puts the story in the forefront.
The game does include advice/rules for campaign play - which could refer to the horror or to the witness or to both.
The game itself has a clear structure with three roles that are rotated after every scene: The narrator, who is the game master, the witness, who plays the one and only player character, and the watchers, who work as kind of assistants to the narrator adding atmospheric details to the narrator's description and playing NPCs in multi-NPC situations to lighten the burden of the narrator. The roles are clearly defined and each one has their space within the narration. This, in turn, makes this unusual game relatively easy to play and keeps things orderly. Having just a single NPC keeps players from arguing about what their characters will do next, and indeed, the game itself is in general about narrating separately but building on each other - no one is to discuss what someone else says (unless the rules are violated) and within their realm, each one rules supreme.
With a rotating narrator, any concept of a prescripted adventure is bound to fail. Instead, the game is about an emerging story which is rather cleverly handled. In the first two phases, clues are generated, which are explicitly marked as such. And after each scene, each player is tasked to interpret the clues presented thus far - alone and for themselves without any sharing or discussing. This may seem insignificant, but is actually a very clever design. By actively interpreting the clues, each player thinks about the story and develops a logical interpretation. And when it is their turn to provide clues, those clues are likely to be logical. At the same time, the rules ensure that the clues are not too explicit, leaving room for various interpretations, so that no one can tell where the tale will lead in the end.
This leads to another nice aspect. Scenarios for Lovecraftesque are not complete adventures. Instead, they are adventure seeds with most of the setup information as well as some inspiration for the later game provided, so that even a single seed can be reused and yield completely different tales. And the book comes with a lot of scenarios and there are even more on the homepage, even two that were published in other magazines. So, there is a lot of material you can use for inspiration if you don't want to play a freeform adventure.
All in all, this points above make it also a good candidate for solo roleplaying and maybe also a good game to practice playing/emulating several players while soloing. With the roles being so strictly separated, you are less likely to worry about when one player or the other may shout in. With no finished adventures but rather adventure seeds, it has exactly what you want for normal solo gaming. And the clue mechanism yields itself to forcing you to explore different lines of thought and in the end surprising yourself. Finally, the lack of stats can be refreshing as you don't need to stop to consider whether climbing that wall is a difficult or very difficult challenge. Mind you, soloing is not an officially supported option, but I think it shouldn't be too much a problem with some outside material like a player emulator, oracle, or random content generator.
My vote is that it is a recommendable product, especially for solo gamers, despite its flaws.