It starts with the complete original text of the general prologue, with line numbers (helpful when quoting/reading notes), but the best bits are the notes. They give an overview of each section (e.g. The knight) and then line by line analysis for most of the lines. This isnt just a translation, but it also explains why Chaucer may have written it, and what it shows etc.

There is then an excellent section on Chaucer's approaches, (namely approaches through Chaucer's life and times, through Chaucer's subject matter and through Chaucer's poetic technique.) This is written in a fairly casual manner, and is therefore relatively easy to read through. It also includes activities and discussions, if you're feeling eager!

Finally, at the back of the book, there are notes on Chaucer's english, explaining the actual grammar of middle english. While I did not use this as such, it was still interesting, and I have never seen any similar feature in other Chaucer books. It also includes notes on how to pronounce the words typical to Middle English, in case the idea of reading it out loud suddenly appeals to you.
The book ends with an almost exhastive glossary, which comes in extremely useful when attempting to translate the text!

I would certainly recommend this to anyone studying, or with an interest in Chaucer.