I bought this book for my English lit AS level, and found it extremely useful. It contains a comprehensive selection of Owen's poems and letters to his mother, background about Owen's life and WW1 and also notes on all of the works included.
The notes are most useful as a supplement to notes learnt in school, as they are quite obscure but contain fascinating ideas and references which most other students would probably not know about. Although I was only studying poetry, the letters were also indispensable as a source of information on Owen's life, thoughts, and most of all the experiences which inspired his poetry.
Overall, a must-buy for A level english and also for anyone interested in WW1 poetry as it makes a very interesting read!