The book is not their best handbook. It would be about 5th. And really does not have any good kits like the thiefs or Bards etc. The main thing to note is that D&D is now heading toward its 4th edition; and this book is for the 2nd. So really not practical. But can only be used for background.
This handbook has a good chapter on roleplaying mages and on spell research as well as spellcasting under adverse conditions. This book is good for customizing a campaign or making new spells, items, or schools as well. There are also a couple of new spells.