I'm able to review the 4th edition versus the 3rd edition. The new edition contains the additional topics: Data Center, Video (included with VoIP), Final Prep at the back of the book, and "Memory Tables". "Memory Tables" are interesting in that they would be the 50 or so pages I would print out and use as my "Book Notes". My study method includes the writing out the notes from the book, and my notes would go on those pages. The new edition has dropped IS-IS (just in case you were looking for that topic).