The cover illustration shows a mage who is either a bit baffled or trying to keep a straight face whilst a bunch of small rocks orbit his head... or maybe he's wondering if he had one ale too many? It makes an excellent introduction to that most bizarre of magic items: the ioun stone.
Stemming from ideas in Jack Vance fantasy novels, they are quite a difficult concept to get your head around. This work opens with a delightfully in-character discourse on the sheer lack of information about where they come from or what they are before launching into descriptions of some thirty of these doo-dads. Apparently Questhaven, the default setting for much of Rite Publishing's work, is a hot-bed of ioun stone manufacture, with craftsmen and mages combining to produce ever more exotic items for the discerning practioner. The assumption is made, however, that you know what they are. Now, true, they've been in fantasy gaming, especially Dungeons & Dragons, for a long time... certainly AD&D 2e if not before, and basically are magic items which operate when within 3 feet of their owner and, yes, they do fly round his head - the advantage of this being that they don't occupy an item slot. Over the years various rationales have been given for their origins, Vance himself wrote that they were acquired from the heart of a dead star, whilst the Postive Material Plane has also been cited as their source. From D&D 3e on, they can be created in the same way as other magic items. Each one confers a specific benefit based on shape and colour, the effect being automatic as long as they are orbiting their owner's head, and even when expended they can give a psionist a single point of power.
Enough of the background for anyone unfamiliar with them, on to the contents of this book. There's a whole range of intriguing effects available from the different stones detailed, plenty to whet the appetite if you are looking to acquire a few, or want to learn how to make them... or if, as a GM, you want to scatter a few around as treasure. Try a Powder Blue Sphere Ioun Stone, for example: once per day you can use it to send a message of up to 140 words to someone, then on to someone else, or even back with a reply. A magic text message or tweet... or if you have a Translucent Ellipsoid Ioun Stone, you can transform yourself into an amorpheous liquid form once a day. Others confer combat bonuses, or enhance skill check rolls, each quite specific, so choose wisely when you go shopping.
There also is an unique one, called The Master's Finch. Said to be imbued with the spirit of a druid's familiar (who was a finch), as its owner rises in level new powers manifest. Indeed, it appears to be able to learn, for it is told that each new owner finds at least one power that has not been associated with it before.
Ending with a handy reference table, this is a nice collection of stones to add to your game in various ways, a fun little catalogue well-presented and explained. Just don't give one to someone who's drunk, they will never believe that they are not seeing things as it whirls around their head!