It has an earthy, rich flavor, and in some cases, an acquired taste. I am not sure of the tannins, but I believe that the aging process mellows them. The tea comes inexpensively, but the older teas are a bit more, and are sold in cakes. The less expensive ones I find are sold in bricks.
Some varieties are sweeter and more mellow than others. I am currently drinking a MGH Menghai ripe tea, and yesterday, a green tuocha "mushroom." They are made into different shapes, mostly dependent upon price and region. ...or maybe boredom, on the end of the tea makers! LOL...I usually have to be in the mood for a puerh, and it is at those times that I need more grounding, and some detoxification. It also happens at seasonal changes, take autumn, for instance.
To make a good cup of puerh in my eyes, simply take about a teaspoon or two into a quart sized teapot. Rinse the leaves with a bit of boiling water for several seconds and pour off. Then pour a cup or so of boiling water onto the leaves for about 10-15 seconds and pour off to drink. This is your first cup, prior to your meal.
Eat. Make your second cup by pouring boiling water on for a bit longer this time, maybe say 30ish seconds, maybe a little more depending on flavor. With my strong green tuocha, this is plenty. For my Menghai, I prefer a little more time. I drink this during or after the meal. Once again I pour on another two cups and I let the brew "stew," as the English say, when leaving tea leaves in water for extended periods of time.
The flavors by then have gone through all their seasons and may be time for a new spoonful of fresh leaves, if one wishes to continue drinking.