Geoffrey McKinney writes well. The imagery he draws with his written word compliments the art and the physical presentation (assuming you are reading a dead tree copy and not a PDF). He writes over the top, and he writes it well.
The ideas presented are the key here. Carcosa (so far - I've yet to reach the halfway mark) is one of those rare products where the parts are worth more than the sum.
I don't see myself running a campaign where Hit Dice and Weapon Damage are decided at the beginning of every battle - it adds too much randomness, too much bookkeeping, especially in the OSR corner of the hobby, where streamlined and basic is generally considered better.
Would it work as a diversion if the PCs get sent to an alternate dimension? Definitely. This is one of the reasons I think Carcosa is worth more for it's parts - as a toolbox / sourcebook hybrid - than a campaign setting of it's own.
Geoffrey has similar feelings, or at least expects a large number of readers to feel the same:
There is no right or wrong way to use Carcosa. Please
feel free to add to this book, or to delete or change anything
within. There is nothing in this book (or anywhere else) that
is “official” Carcosa. Following are only some of the possible
ways to use this volume:
ЖЖUse it as-is for a ready-made campaign.
ЖЖThe player characters in your regular campaign have
been transported by a curse to a terrible location:
ЖЖUse Carcosa as a change of pace or for one-shot games.
ЖЖCherry pick contents (whether monsters, the psionics
system, the dice conventions, various encounters, the
sorcerer character class, or etc.) to use in your regular
ЖЖSimply read the book as inspiration for your own
Above all, enjoy yourself.There's a lot of stuff to borrow and steal. I'll try and hit on it in the next part of the review.