I picked up both new books yesterday when they came out, Bigby Presents.. and this almost complete guide to dragons and so far I think this book has been the biggest disappointment. The useful information for the book is mostly just dragon habits, likes and dislikes, lairs and that's about it. here won't be any new class options, player options, etc. it's mostly lore and artwork.
There's a little bit of dragon lance lore in there like Tiamat and Bahamut have different names across the planes but I didn't see any kind of "new" dragons (Dragons from older editions brought back" The lore was kind of bare bones for most probably being from another book like fizban's or there Manuals. I can't say for sure on all the art but they also defiantly used old artwork from not that old books. I think the shadow dragon is the same from fizban's book. The kobold treasure photo is from Tyranny of Dragons. So it seems like they defiantly made some new beautiful artwork but also just used old artwork in it which was disappointing.
I would only add this book as a piece of your collection, If your buying books and want to know if this is a right away buy then just hold off for a needed supplement like Tasha's, xanathar,etc.