What a gem this is!
The core of this is a series of submission guidelines to authors of solo adventures written by Mike Stackpole, plus additions from Ken St. Andre and Rick Loomis. These guidelines aren't just tips on writing solo adventures, they are excellent guides to writing any adventure, for any game. They cover creating flexible adventure paths that avoid railroading and repetition, creating interesting approaches to failure that leave characters open to more adventure. They cover making adventures resilient to powerful magic items and spells, as well as maintaining an adventure at a heroic level, rather than devolving into choosing directions to travel at random.
There is also a collection of the magic items that could be awarded from the early Tunnels and Trolls adventures, all collected in one place. This is a great resource for T&T GMs wanting to add pre-existing items to their games, or as a list to compare against when building something unique.
Though brief, this is chock full of information. The bulk is written by Mike Stackpole, after all, and the one page guide by Ken St. Andre that adds to this is also rich in guidance for an adventure author.
Anyone writing adventures either solo or GMed for any system will find this to be a treasure box!
[5 of 5 Stars!]