This review is sponsored by
Gaming Frontiers
In essence, the Grimoire is a simple book. It provides a new spellcasting system in addition to the spells to go along with it. As a standalone product, it suffers the same issues that Way of the Staff does in that there are many references to things not covered and doesn't stand on it's own as a 3.0 or 3.5 product but can still add some interesting ideas to any campaign.
The book is broken up into two chapters, Magic and Spells. The first chapter provides definitions for the many terms used in Arcana Unearthed. Spells fall into levels, just as they do in standard 3.0, but they also fall into simple, complex and exotic spells. Those spells also follow the schools that we're used to from 3.0, using abjuration, necromancy and others of the eight standard schools. The descriptions are modified with things that are familiar, like fire, to things different like psion.
Spells do not need to be kept in a spellbook but must be readied. This is similar in some ways to a cleric in that the caster can know these spells and change what they have prepared to cast. The main strength of this spell system though, is the flexibility. For instance, spell slots can be moved around with quite a bit of leeway. For example, you can take three spells slots of the same level and turn it into a spell slot of a higher level, or take a spell slot of a higher level, and turn it into two spell slots for a lower level.
You can cast spells that are heightened, using a higher level spell slot for a different effect, changing certain aspects of the spell, or diminished, using a slot one level lower, and effecting the spell in a negative way like reduced damage or range. This system is perfectly useable in and of itself and the spells latter on serve as good examples.
Some other gems in this section include spell catalysts. These devices are often gem stones or other valuable treasures that are consumed in the casting and add various effects to the spell even as they are destroyed. I know most players won't hesitate to throw an emerald worth at least five hundred gold pieces into a spell for an extra 2d6 damage. The only bad thing is that there is less than half a page of examples and it's not clear on if you can combine catalysts or if there is a limit. I'd probably impose a limit of no more than your bonus modifier.
The problem comes with things like spell Templates. There is a key section that mentions the term laden. Now laden means that you cast the spell with two slots of the same level, so for example, in a standard game, you'd use two first level slots of make a magic missile spell laden. I say this is a problem because while it talks about what the various spell templates do, it doesn't actually provide the feats for them. So the question is, does a blessed spell require the user to make it laden? You'd never know as the book only states that this effect is gained from the Blessed Mage feat, which isn't detailed in this book.
Another problem is the spells. Unlike standard D&D these spells aren't broken up into different types (arcane and divine). Perhaps it's just that part of me that screams, “Why separate the classes from the system?” You can't use these spells straight in a normal D&D game. Sure, Bast is a nice 0 level spell that could probably be used for arcane or divine list, giving only a +2 bonus to your next attack roll, but other spells blur the division in D&D that mages do damage and clerics heal and have more versatility.
Take Regeneration, an exotic 8th level spell. It restores lost limbs and body parts but such a spell would normally be beyond the reach of almost any mage. Not so here. As a matter of fact, there is no real healer set of spells, although some spells can heal, just not in the fashion that standard D&D spells do.
The spells, for the AU game are great as they show how many of the standard spells work in this different setting with it's different rules providing the GM with a solid guideline but without the conversion notes that are in another product, making this a total of three products you'd need to use this product with 3.0 without overbalancing your game, is it worth it?
If you want to see more variety and options in your game, yes.
If combined with Way of the Staff, this is a 4 star product but it's reliance on that book for feat descriptions and the classes to go along with these spells hinders it's stand alone use, especially if you just want a book of spells for your D&D game. Be aware that conversions will require work but should add a lot of variety to your campaign.