I have re-rated it, since it's an outdated edition.
Get the revised one from 2011. Sold all over on the internet for $12.95. Including from the current publisher. Type in "What Happens at Mass revised". This is an excellent book. It is better then most other books out there on the mass. I run a parish library so I get lots of feedback. This book is by far the most popular. The problem is this is NOT the REVISED version being sold by LTP Liturgy Training Publications for $12.95 on the internet. So fellow catholics, if you want the book "What Happens at Mass" revised edition by Jeremy Driscoll, with the NEW 2011 LITURGY (MASS) CHANGES don't purchase this copy. This is the ATMASS copy, not the ATMASS2 copy.
If you want this just as a collector book, go ahead and buy it.
Onto the review: it has 5 chapters: Laying the Groundwork, Introductory Rites, The Liturgy of the Word, The Preparation of the Altar and Gifts, The Eucharist Prayer, Communion and The Dismissal Rite. I can say more about Jeremy's book but many of the other reviews already state it.