James Joyce devoted 16 years to the "Work in Progress" that was published in 1939 as Finnegans Wake. The new "restored" edition published by Penguin Classics represents an alternative outcome of Joyce's process, thanks to an even longer process of investigating the drafts and notebooks he left behind. Editors Rose and O'Hanlon (along with other scholars) have been following Joyce's voluminous paper trail for over 70 years now, and out of that deep immersion have produced a text which arguably realizes Joyce's intentions better than the first edition did.
As the editors explain in their Preface and Afterword, this is an alternative to the original edition, not a replacement for it. And it's meant for readers, not mainly for other specialists. If you found Joyce's masterpiece unreadable before, this new edition won't change your mind -- but if you're familiar with it, you will probably notice the difference even in the first few pages. Among the 9000 changes to the original printed text, some are corrections of definite mistakes that had been overlooked, even by Joyce himself, who was nearly blind by the time he made the "author's corrections incorporated in the text" of the 1958 printing, the one i've been enjoying for about 40 years now. But most are better described as alternate readings which could just as well (or better) have emerged from Joyce's complex process, even though the previous readings were not simply wrong.
This "restored" edition might be even better described as "refreshed". It's not meant for scholars who want to see the reasons for the changes or systematically compare the two alternative texts, but for readers who want a fresh experience of the Wake, whether they've been through it before or not.
For this edition the whole book has been totally reset, which has never happened before. The page numbers don't correspond to the old one -- we have 493 pages instead of the 628 of earlier printings, to which the standard citation method refers -- and some have complained about this, but it shouldn't bother the average reader (if there is such a beast as an average reader of Finnegans Wake). Apparently scholars referring to this new edition will cite it as "FW2" for short. The format is larger while the font size appears to be the same (a bit too small in my opinion), hence the smaller number of pages. A couple of appendices explaining the project that resulted in this edition are included, along with the aforementioned Preface and Afterword, but the rest is all pure Joyce.
I'm about to begin my third wander through the entire Wake, and with this edition in hand, i'm anticipating untold wonders and joys of night-revelation. That old shapeshifter is more alive than ever.