Okay, let's first get the art out of the way. Indeed the only pieces of original art in this book are the cover -which is a beautiful work of art- and the maps of the empires of old. And personally, I didn't like the art style of those maps. The forests on them were very detailed, while the mountains were not, and the rest of the maps (desert, plains, water) had no detail at all (just one bland colour).
BUT, important to know for the fans is, how come? Why did they only re-use existing art? The designers went on a leap with this book. They knew some hardcore fans would want it, but they weren't at all sure about the general public. So they got a very tight budget to work with. The book took a lot of writing work, being filled from front to back with one humongous small print timeline, plus all sidebars. Naturally, a very very low art budget was left. They decided to spend all of that little money on the new maps, as they would be most important, and re-use existing art to fill up the rest.
I think they made a wise decision at that.
The rest of the book: The timeline is complete. After a one page foreword, and a one page introduction and guide for calendar conversion (ex: the Mulhorandi calendar starts with the founding of Skuld) they jump right in at -35.000 Dale Reckoning. They cover the empires of the creator races first and go all the way through the history we know, and further. They end in 1385, thus giving sneak peaks into the 10 years that still have to come; to show a glimpse of the events that will have taken place between the 3rd and 4th edition realms.
Halfway through the book they give some pause from reading the extensive timeline, by giving lists of lines of monarchies from various dynasties in Faerun. Somewhat like the lineages in the appendices of Lord of the Rings. Throughout the rest of the book, sidebars with stories take over this function. These stories are mostly written in character. So during the crown wars, you may run into an excerpt from the lore gem of house Aelryth of Miyeritar. Later you read the lecture about the Dawn Cataclysm, by a priest of Lathander. etc
A minor nitpick on these, is that many are written in hand written fonts. A minority of these ended up on backgrounds that made them somewhat hard to read. The majority were just fine though.
One final sometimes handy tool they added to the timeline, are dates attached to certain names. These dates point to the previous and following year in which that same name is mentioned. So if you are trying to trace one particular chain of events throughout the timeline, this tool will greatly help you.
Lastly, the writers give some new information on various events, scattered throughout the timeline. One of the sidebars throws an interesting light on how the sundering created Evermeet for example.