First, the good:
David Norton has done an incredible job restoring the King James text to it's original, intended form. Even the 1611 first edition contained errors, so this is really the first time that the translators' intended version has appeared in print (approx. 400 years later).
The layout of this book is a joy to read - instead of each sentence appearing as a paragraph, the original translators' intended paragraph layout has also been reconstructed and restored. Additionally, all of the songs and poems that have always appeared inline as a continuous stream of text are now broken out with appropriate spacing and line breaks, actually appearing as poems or songs.
Mr. Norton also updated all of the 17th century spelling to the modern form. Unfortunately, his definition of "spelling" is very liberal:
Changing "witnesse" to "witness" makes sense, as it is merely an updated spelling. Changing "digged" to "dug" or "spake" to "spoke" is debatable because it alters the flow. It's not just updating the word's spelling, but updating the word's conjugation.
The most egregious changes were when he changed every occurrence of "thine" and "mine" to "thy" and "my". For instance, "...to whom thou sworest by thine own self..." (from Exodus 32:13) is now "to whom thou sworest by thy own self." "Thy" should always be "thine" when the following word begins with a vowel instead of a consonant - this is basic English grammar, and the new text errs.
As an example (Psalm 141:8)
The traditional KJV:
But mine eyes are unto thee, O GOD the Lord: in thee is my trust; leave not my soul destitute.
But my eyes are unto thee, O GOD the Lord:
in thee is my trust, leave not my soul destitute.
"mine" has become "my", an alteration of the original grammar rules. However, the new layout of the text for the psalm as a whole is a valuable addition and the new sentence is beautiful in its own way.
So overall, the "updates" do make for a smoother and faster read, which some people may prefer. Combined with the improved layout, this version of the KJV is a pleasure to read.
As an alternative, if you prefer the original spellings and grammar, but want the apocrypha, then the only option is Oxford's The Bible: Authorized King James Version (Oxford World's Classics) which is also a paperback with a colorful cover. Unlike the edition published by Penguin Classics, Oxford's is the traditional text; but suffers in that it does not have Mr. Norton's improved layout.
Penguin Classics/David Norton's version: Has reconstructed original text with excellent layout. Grammar changes, quotation marks, and removal of italicised words make for a faster and easier read but introduce new frustrating errors.
Oxford's version: Is missing Norton's reconstructed text and his vastly superior layout, but keeps the original grammar.
These two books are the only paperback editions of the KJV that contain the apocrypha.