David Block 
Social Turn in Second Language Acquisition [PDF ebook] 

This book offers an extended critique of one of the main theoretical approaches to second language acquisition–the input/interaction/output school–on the grounds that it does not take sociolinguistic considerations into account. This boils down to a social approach that complements the dominant cognitive approach. Block’s approach, in essence, is to walk through the definitions of each part of the term ‘second language acquisition’, which is more substantive than it sounds, to broaden future research in the field.