I've used Haynes and Chiltons for my older American cars (cavalier, windstar, explorer, etc.), but the Bentley is the best for the BMW.
Get the E30 for the body and the E36 for the engine (two separate manuals)...you will find that it is MUCH worth the $$.
Look on Ebay/Amazon for used manuals--the E36 one will cost a good bit but helps a lot.
AFARR
(The above info is assuming you have an E30 318is).