Bloomsbury Publishing 
The Continuum Companion to Second Language Acquisition [PDF ebook] 

Bloomsbury Companion To Second Language Acquisition, this book is designed to be the essential one-volume resource for advanced students and academics.
It offers a comprehensive reference resource: it features an overview of key topics in SLA as well the key research methods. It then goes on to look at current research areas and new directions in the field by examining key relationships in the field, including the relationship between first and second language acquisition and the relationship between L2 input and L2 output.
It is a complete resource for postgraduate students and researchers working within second language acquisition and applied linguistics.