I think it's fair to call the DLC offerings of the Witcher 3 expansions more than anything else: they add around 30-40 hours of new game content all in all. The first one, Heart of Stone, adds more story to the original game regions, where as Blood and Wine adds brand new area of Toussaint, where the main story takes Geralt to do some more monster hunting as well as poking around more points of interest.
Heart of Stone adds a nice, little tale of mystery to the game. It begins when Geralt finds a notice about a monster that needs to be slain, but after accepting it he finds himself falling pretty deep into the rabbit hole before he manages to come out from the other side. Besides the main story, HoS has also some side quests as well as new rune smith, who can create more powerful enchantments on weapons and armor. The official addition to the game is around 10 hours of game play, but in general it might depend more on how wealthy you are on the moment you start the expansion (which you can do either from the game itself or from a menu with a character created solely for the purpose), as collecting enough money for the rune smith quest might be more laborious of the tasks at hand.
The story content itself is pretty solid little horror mystery, but I must confess I didn't really use the services of the rune smith that much. I did unlock his traits, as to that point I was already quite wealthy, so it was just a question of giving him what he needed, but in the end, I didn't utilize his services.
|Geralt's own vineyard at Toussaint.|
Again the main story begins as a monster hunt, and it does stay that way to the end, it just is that the case at hand has more shades of gray in it and you can, if you want, try to make the ending at least seemingly happy one, despite there's ton of crap that flies the fan before the ending point. Blood and Wine also acts as a final chapter of of sorts in the tale of Geralt and Yennefer, though you can still continue completing the unfinished business after the end if you so choose.
|Yennefer taking some much needed R&R|
Even without the DLC, The Witcher 3 is among the best open world games out there. It has very unique feel about it and the world feels genuine with its folk lore laced atmosphere. Unlike many other RPG's out there, the world of Witcher isn't trying to ape up Tolkien, but is more content on trying to create something different. And what's it worth, I think it works extremely well.
The DLC content for the Witcher 3 is available through GOG and Steam either as individual packages or as a single season pass. The main game is available from same sites. Go get.