The Witcher 3: Wild Hunt - Hearts of Stone Review (SŦĐ Kaas)
This DLC is well worth the cost, and imo one of the best DLCs ever. The content it adds is mostly story-based, but the enchanting mechanic is extremely useful in gameplay and definitely adds a new aspect to the way you can customize your builds. This DLC has what is in my opinion the most impressive storyline out of the entire game and the characters it showcases have some very exciting lore as well as ambiguous morals/backgrounds which make it quite easy to get lost in the theories about them, especially Gaunter. He is probably the most interesting character in the entire game, but at the same time the most mysterious.
Imo this DLC is great, but if you had to pick just one of the DLCs to buy, id recommend the Blood and Wine DLC first due to how much new content it adds. The quality of the content in Hearts of Stone is imo better, but the amount of it is far lower and will have less impact on the gameplay at large, while the Blood and Wine DLC adds a very well-developed new area to explore, with tons of new quests, characters, new gameplay mechanics (your own house, mutations, grandmaster witcher gear, and more.). But if you can afford both, buy both. Both DLCs are simply incredible and masterclasses on how your DLCs should be for any other game studio to look up to (although they usually stray far from this quality....).