I'm late to this party, but wanted to contribute to what I think is an excellent OSR role playing game, and setting.
I picked this up as an aid to Solo roleplaying before GMing my own group, and the final 16 pages are invaluable to that end. The penultimate 21 pages of adventure design are also packed with goodness. It crawled a little for me in the middle, reading the spells (more on that later), but other than that it's a very enjoyable read.
You can read the description for an idea of the setting, but I sell it as Conan the Barbarian + Big Trouble in Little China + Pirates of Dark Waters (the 90s cartoon). Crawford writes with wit and elegance, and explains the rules easily. His setting is such an interesting one (of course there's another source book), that in another time, another world, could have grown to rival the Forgotten Realm or Dark Sun.
So why 3/5? Two reasons but the first of them a bit silly.
I don't like the Spell Names. I said it would be silly.
But just as some people don't like Tunnels & Trolls spells because they sound too 'meta' or glib (e.g 'Knock, knock', 'Take That, You Fiend!'), I really don't like the verbose spell names here. I feel many of them are named so grandious, play would stop to explain what they do, and whilst that could be true of any spell the first time it's called upon, you could probably figure out what 'Magic Missile' does. What on earth does 'Assuming the Flesh of Mist', or 'Crimson Rain of Deliquescence' mean? I don't even know what a deliquescence is, let alone how it affects a crimson rain. EDIT: I broke down and looked it up. I still wouldn't be able to guess what this spell does other than getting people wet on a sunny day.
So, again, it's a silly point, but searching for a new spell to gain takes longer than it needs to ('I want to cause damage to somebody within 30 feet, which one is that?'), and I feel players will eventually shorten or given them nick names.
The second reason, and my biggest gripe, is for the description and pictorial depiction of child corruption and mutilation (I may have buried the lead on this one). One is a child after being consumed by the Red Tide (a corrupting fog that may act as an antagonist or natural barrier), another is a demon pieced together with body parts of aborted or miscarried foetuses.
In a book filled with glorious illustrations, not every monster is depcited, and I think it's in poor taste that these two were chosen. If these 'monsters' had to be in the game, I think the text would have sufficed. Crawford is a very good writer, and his words can be creepy enough.
Now I thought I was a fan of cosmic and body horror, loving films like Society, The Thing, Videodrome, but I guess involving kids is where I draw the line. And I know "It's all just make believe, you were more than happy to hack through 100's of soldiers", but it's not the same, and if either of these were revealed during a game, I would be slapping that X in the middle of the table hard. Yes, it's fantasy, but it's meant to be enjoyable, not some grim slice of the realism of evil and fantasy pestilence might cause, and takes an otherwise mature game in a more twisted direction.
I ordered this in soft cover in the UK, and is one of the few physical books I've ordered from DriveThru POD that arrived in peftect condition with no printing QA issues or mis-aligned covers. The paper is good, thick, and smooth, the text clear, and lineart detailed.
So do check out this wonderful book, It's a good price if you're going to use all of it, but quite pricey if you're only interested in adapting Solo play for another game. There is a Black Streams: Solo Heroes supplement available, and is free, but at half the length of the Solo play chapter in this book, you're only getting 'How to play a duet or solo with existing OSR modules', not crafting the interesting adventures this book offers. Mythic GM Emulator or DM Yourself may be more up your street, but I think the author's written a very clever Duet and Solo system here.
If depictions of child mutilation and silly spell names don't bother you, consider this a 5* review.