The Ring is simply a giant masterwork. Tackling it is like attempting to scale a mountain. And if you're going to do it properly and get the very best out of the experience (and make the massive investment in your time worthwhile), you will want someone with you along the way. And this is where this Companion is a real must.
The introductory essays and the other material are useful primers and help put everything into context (but they are far from exhaustive - more a primer and an aid for further reading). But the real value is the libretto. My recordings come with a libretto, but straining your eyes through a cd booklet is distracting. And then there's the quality of the translation itself - and believe me it makes a real difference to your enjoyment and understanding.
Wagner's language and versifying is deliberately archaic - even in German, so any translation is at first going to appear odd and almost difficult. But follow each line with this companion and you will see that the translation somehow not only captures the meaning, it follows the sense, rhythm, cadences and line length of the original - so as you listen, the english translation flows along seamlessly with the sung lines. After while you are not conscious of translating, but are in the action and going with the flow. And my, when you get caught up the flow of Wagner (with the volume turned right up of course) it is a totally absorbing and genuinely thrilling experience.
What's great too is that there are are references you can look back to later or read ahead and look up, and just enough stage directions added. Too much direction and you can't keep up. Without any you miss vital pieces of information and action - here you can 'see' as well as hear just enough not to miss anything.
A thoroughly recommended piece of work, and really glad I got hold of it before plunging in.