I've been trying to use this basically every day since I got it, pulling up my characters and trying different adventures. I've tried using a module, I've tried going freeform and making things up as I go in a variety of different ways, but basically every time I try to use the product it ends up being a frustrating experience.
On a technical level the book is hit or miss. It's 34 pages, the interior art is ok, but looking at the credits reveals that the only original art piece is the cover which is... fine, I suppose. The interior is riddled with spelling errors, up to the title itself (it's given as both "Crusaders Solo Handbook" and "Crusader's Solo Handbook"), and though it doesn't get in the way of understanding the product, it still stands out. The book mostly uses a simple column style, except for pages 12, 13, and 15 which, for some reason, use a strange half-column layout that's actually more annoying to read than one would expect.
The contents itself... well, the first page has an introduction and a sidebar, but both say pretty much the exact same thing. It is hardly necessary to have both. Getting to the actual meat of the product, it explains that the real basis of the product is improvisation, and it gives three tables (technically four and... well, I'll get to that) to help. Unfortunately, the tables are so basic that it mostly leads to frustration. It has very few suggestions to help guide you, most are simple and are often repeated a couple times, and the amount of pre-game prep is never really explained. How much do I need? Have I been doing too much or too little? It is explained that you break the game up into "Scenes" but it's also noted here and there that one should have a list of scenes, sometimes suggesting a pre-designed set (especially for modules, though again it's vague on if you should have a list ready to go even if you're not playing with a module). In many ways it feels like trying to write a story rather than play a game, which is something I enjoy but is a very different activity to playing, even playing a TTRPG like C&C.
The actual mechanics are pretty simple, you have Closed Questions, i.e. yes and no with three results (No, because...; Yes; and Yes, and...), which works similar to the "SEIGEengine" [sic] mechanics of C&C, but without an ability score, just the d20 and your character level. At various points, such as rolling a '1' or a '20' or when the CB hits 20 or more, there is a complication. A complication is whatever you want it to be ("Complications are the perfect time to take the first thing that comes into your head and build it into the game"). Rolling a '1' is a particularly bad complication and rolling a '20' is a particularly good one, while the ticking CB (it climbs by 1 each time you roll a 'No, because...' on the Closed Questions table) is just a complication.
Open Questions are for things that aren't yes or no questions. You roll 2d20, and one die is the first half and the other is the second, giving you results like "Scheming with alchemy" or "Lending aid to old lore". What that actually means is, as you might have guessed, all improv. It ties in with the next table, on NPC reactions ("[...] for NPCs it is always worth rolling a 2d20 Open Question roll. Use this as the NPCs [sic] deepest desire, motivation, or personal goal"), so you roll another d20 and find their reaction. Then you improvise what that means. The example given has an error that's minor but silly, a roll of 19 should be 'alchemy' and not 'magic' but the example goes on as though 'magic' was rolled.
After that you get an explanation of how to use the Scenes List (use it to keep track of scenes), NPC List (use it to keep track of NPCs), and Loose Ends (whatever's left over that might possibly be used in a later game). There's a lot of words, but very little being said. Next we get the Progress Clock, which might be a neat and simple way of having a time pressure but every time I tried to use it I would manage to roll phenomenally well and not had it tick down.
Next we get a section on Combat. The first part has some decent advice for manipulating the numbers of enemies one would normally meet in a regular encounter, but then we get the section on Narrative Combat which is so vague as to be completely useless (after spending far too long trying to figure out what it actually meant, I stopped trying and used standard combat), and a section on Solo Combat which doesn't say anything new nor anything interesting. There's a section on Traps and Riddles but... well, "[i]f you are setting the riddle and you know the answer, so does your character. You can reduce the riddle to a CB roll, but I don't think that adds much to the game." It's a tricky subject, but I'm not sure handling riddles like that adds much to the game either?
After that you get sections on things like Experience (story experience is recommended), playing around with flashbacks (one of the things that's easier to do in solo gaming than group gaming, though its use here seems to be more how to give yourself a previously unknown edge when the dice turn against you), keeping a journal of your adventures, using the Closed Question table for world-building, using the handbook for group play (if the DM/GM/Keeper's gone and nobody wants to run things?), and using these rules for a published adventure. It's less useful than it sounds. There's a bit in the section on modules that sounds like at one time there was a deeper system for Keeper Emulation, since it mentions that some results may lead to "xxx end the scene" but that is not, in fact, a result one can roll.
After that we get a section of Playing Advice, which gives options for starting at higher levels (Start at level 3, but with 0 XP so you have to go enough XP to reach level 4 before you get to level up is the example used), Fate Points (I'm personally not a fan of that mechanic, but it gives several options for using them), and the player always getting first initiative unless surprised (the only one I used). This is followed by a page for NPCs, a page for Scenes, and a page for Loose Ends ("Thread List" as it's labelled here).
Then we get the Alternate Open Question Prompts. Instead of rolling 2d20, you look up, choose something in sight with a two-word name and use the first letters (example given, "Tea Cup" gives you 'T' and 'C') to select from a 9 page word list and interperet the combination you get. It is awful to look at, hardly stimulating, and I have no idea how useful "CB radio", "E-waste", "New York", or "Zabadabadoo!!" will be. I guess it probably works, but it really feels like it's there to fill out a page count. After this you get the last real table, Magic 8 Ball Answers. It is exactly what it sounds like. The book wraps up with the OGL and a blank page.
As I said, it's been a frustrating experience. I never thought I had much issue thinking on my feet, but this product makes me question that and frankly, my capabilities as a DM (not, uh... not great). I'm not quite sure who the Crusaders Solo Handbook is for, the people it seems to speak to most (improv people and writers) are also the people I'd assume aren't in need of the product, or at least not the product as written. The three main tables, Closed Questions, Open Questions, and NPCs, feel like the start of something useful, but also don't hang together in a satisfying way. The advice and explanations are over-written, repetitive, and rarely particularly useful. The formatting is standard, except where it isn't. The quality of the product varies and it is rife with errors. It's not a 1-star product completely void of use or promise, but it needs so much more polish to reach the 3-star mark or higher. The Crusaders Solo Handbook is something I want to like, but the result as-is doesn't reach the heights it needs to.
For the record, if you, like me, wanted to know what Stephen Chenault had to say about this, it's at 18:33 on the hour-long video on the store page.