few of the good book to improve english communication skills are :
Word Power made easy : Norman Lewis
English Grammer : thomson and martinet
Essays by samuel Smiles (3-4 books) (an essential set of books , i must say due to its superb composition and usage)
Write Better , Read Better : Reader's Digest Publication (for those who have good command over vocab and grammer ) (again an essential book)
In addition to above , Kev Nair's course can also be considered.
ll get back to you with few more names i m not able to recall rt now.
10th September 2005 From India, Madras