I consider it really difficult to review this product.
Why? ... Well, before me I have a well designed book counting a full 172 pages with information about spellcraft. It has some interesting headlines, a professional layout and some nice pictures.
It ist advertised as "The definitive d20 System resource for spellcasters" but after reading through it all I can only say: definitely not!
Why? ... Well, to put it simply: There's absolutely nothing within the pages of this book to even get somewhat excited about.
Spells & Spellcraft chapter one promised me over 100 new spells. To be honest I didn't count them. There are indeed a few spells. Most of them are listed with all spellcasting classes and I doubt counting them only once will end up with 100 new ones. But it doesn't really matter. Matter of factly I wouldn't call any of these spells "new" but perhaps "somewhat new". There's nothing really new about any spells in this chapter and you will miss none of them in your game. Most are simply slight variations of existing spells or of spells from other schools of magic. They definitely will not add power or variety to your game, as advertised. Some are not even basically tought-out like the 7th level spell:
Protection from Wards: The character is rendered invisible to a ward, and is completely protected from all ward effects and spells. The ward cannot detect his movements or actions, and he is considered to have an unbeatable SR against any effect or spell generated by a ward.
Surely a nice spell to have along if you are about to breach some highly warded area.
The other chapters of the book seem to be utterly useless to me most of the time. I didn't even find an interesting idea to use with my games. I'll try to explain that in more detail: Let's take the part about libraries and personal libraries for example. I think most of us have an idea what a library is and what book are. Nonetheless most of the chapter describes all these facts again in full detail. In the end you can summarize the whole chapter with those two small tables listed about the text. Some percentages for finding a certain book or information depending on the size of a given city or library. Nothing more, nothing less and nothing you cannot come up with yourself in a few minutes or by simply guessing the chance.
Something like that can be said for all the following chapters. Many words about nothing and I consider most of them useless. The whole chapter about laboratories and research - exactly the same as with libraries. The whole chapter about relics - just another name for artifacts with nothing new. The whole chapter about cooperative magic just a simple feat to allow a character to cooperate with up to one other spellcaster - the benefits seem more than doubtful. And so on and so on ...
To sum up the content: You'll miss nothing if you haven't read it. For the price of $5,00 I do not feel cheated, but I also haven't got any new resources.