A very cool book for retro gamers, but can readily be adapted for 2nd, 3rd, or 4th edition games. The rules are for 1st ed AD&D or original D&D (both sets of rules for each item entry).
Simply put, the book is page after page of magical equipment that isn't found in any other volume. Most of it is weird, most has an interesting backstory, and most of it is highly specialized equipment. It could add a delicious bit of flavor to any campaign, especially a silly one.
There are weapons, vehicles, household conveniences, and every other type of wondrous device you can imagine. Most are ruinously expensive and all have dangerous side-effects or hazards. They each include a description of operation which makes plain the magical "logic" on which they are based, and how the spells placed upon them achieve the desired magical effect. Also included are suggestions for placing the items in your campaign and how to structure adventures around them. The book makes for fun reading, and I will certainly be adding some of these inventions to my games.