the bently manual is a great start to the do-it-yourself"er" it will give you a very decent insite to the complete workings of your car. however dont be misslead by any book that is published . untill youve seen most of it done you'll know right away that the book is only considered a starting point in trouble shooting and repairing. i think EX-tech can vouche for this one.
my personal experience helping at an all bmw garage has shown me and also advice and hear-say from the mechanics , is that its only a starting point. (combined almost 100 years experience between 5 mechanics)
all in all i still agree "pick it up!"