I was required to read this book last year as part of my Masters degree course, and admit to wondering how it could help me. At this point in my studies, I thought I'd cracked it with essay writing, and I wasn't sure that a book could teach me how to write better. Wrong! It has proved absolutely invaluable - I've returned my library copy and bought my own.
The really useful thing about this book for me is that it's directly relevant to English Studies. It covers such subjects as how to choose a literary text to study, the differences between critical editions and where to start with research. It has very useful advice (which I've put to use) on the process of writing. One of the most useful tips was to keep a piece of paper nearby when writing an essay, which states the hypothesis and a brief statement of ideas so far, which should be regularly updated. This really helped me to keep focused on the question and not drift off.
I would recommend this book to all literature students - especially if you are studying beyond undergraduate level.