Academic Vocabulary in Use (Michael McCarthy and Felicity O Dell, Cambridge University Press) is definitely a book that you should think about buying if you are studying at university or preparing to study at university. It practises key academic vocabulary in context. The book is divided into units such as 'Making a Presentation' so that all the key vocabulary for particular functions is helpfully grouped together. View the Contents pages of the book here at the Cambridge University Press catalogue. A very good self-study book.
English for Academic Study: Vocabulary (Colin Campbell, Garnet) is another good book focusing on words from the Academic Word List. The difference between this book and Academic Vocabulary in Use is that this one is more concerned with word forms and word building using the specific words which make up the Academic Word List. This book is more advanced than Academic Vocabulary in Use. If you are a more advanced student wanting some serious language study on word grammar this is the book for you. See a sample unit from Garnet Education here.