I too have not been impressed with any of the solo diver books. Most of it is obvious stuff that any experienced diver should be able to quickly figure out. It's just some guy trying to make money off his hobby by writting a book. Heck, not that I'm all that, but I even considered writing a solo diver book myself years ago. One rainy afternoon, I gave it serious thought (I even went as far as to create a chapter outline). Then, I realized that there really just isn't that much to write about. Most of it would just be an expansion of that which divers should already know. And, it just isn't necessary. Are there any books on solo hiking, solo mountain biking, solo flying, solo boating? No...
I too agree that if you're diving off a charter boat, that's not 'full' solo. If there are other divers in the water that can pull you out and evac you, then you're not fully on your own. Neither is Instructing a class. As little as you may think of divers in training, don't forget some of them are Doctors, Police Officers, Firefighters, Nurses and just Joe Plumber. Dispite being a neophytes to diving, anyone of them has a good shot at getting you to the surface if you have some unexpected health issue. (And, they all have octos from which you can share air.)
Just like OW, AOW, Rescue courses, there are varying degrees of solo. There's everything from same ocean diving off the back of a charter boat, the lowest level of solo, to being far from shore with no boats around and having the weather and sea conditions turn on you, conditions where if you can't make it back on your own, you aren't coming back. There's also 'cave' solo, etc. In that wide range, there's lots of room for people with different threasholds of risk tolerance.
As much as I enjoy solo diving, I will never get solo certified. First, it just isn't necessary. And, second (this may sound egotistical), but I absolutely refuse to take a solo diver course from an Instructor that in all likelyhood has less solo diving experience than I do. Their 'stamp of approval' would have no value to me and just as likely no one else either, including dive ops which is the only place you need it to begin with.
BTW, did I mention that all you solo divers are gonna die. Unless, you read my book of course...