This is a review which is tricky to write because I know most of my readers don't know what yuzu is. Even if I tell you that it is "Japanese citron", that doesn't necessarily convey much as it's about a fragrance and a flavor which are unfamiliar to those who haven't been exposed to it. Taste-wise, the best I can say is that it's a little like a tantalizing three-way between lemon, grapefruit, and orange, with the first two dominating the flavor menage.
This is often sold as "marmalade" rather than in the form I'm reviewing it as here. And even this is not actually marketed as "jam". The characters on the jar do not say "yuzu jam", but rather "yuzu tea". The reason for this is that it is common in Japan to use this marmalade for a tisane. It's a little like the way that Russians sometimes sweeten tea. You stir a spoonful of jam into hot water.
However, I would not waste a precious spoonful of this by diluting it into hot water. Unlike orange marmalade, which I find vile and bitter on a bad day and barely tolerable on a good one, this is much more palatable with a delicate balance of citrus bite and sweetness. Whatever bitterness there is is balanced out of the equation, but the qualities of the fruit stop it from being cloying. The truth is that, I could eat this by the spoonful if I were inclined to allow myself. I couldn't eat the entire jar at once, mind you, but I could put away 2-3 spoonfuls at a sitting before I'd feel overwhelmed. It's just like candy to me.
Note that this is a pretty high quality yuzu jam compared to what is on shelves in most markets in Japan. This is 250 grams/8.8 oz. for about 800 yen ($9.60). The reason it is so expensive is that it is made with honey and because it is made with more yuzu. Usually, there are stringy bits of peel in a sugary base. This is more like a puree so the concentration of yuzu and the sugar component (honey) are higher quality and therefore more expensive. The nutritional profile is almost certainly better than the cheaper versions, and the flavor is a bit nicer, but I can't necessarily recommend this for a casual consumer.
Incidentally, this jam came directly from Tokyo, and it can be bought online as well, but I didn't make the purchasing decision. I asked my brother-in-law to buy some yuzu marmalade for me and carry it over when he came to the U.S. for a holiday visit and he brought me two jars of this. It is fantastic, but I'd be too cheap to make such a decision for myself.
Though I relish eating this straight or on toast, pancakes, or scones, I can't speak for others. I can say that this is delicious and I'd be surprised if anyone who likes something which is similar to candied citrus peel (lemon, orange, citron, of course) would not enjoy this. If you're looking for a holiday treat for a foodie in your life, this would absolutely make a high quality and unique, but approachable gift. I imagine a really upscale eater would enjoy it with certain types of cheese or a good cracker.