Since I learned about this in my beekeeping course I now prefer my honey to be crystallized. I'm a firm believer that if it doesn't crystallized at some point then it is an inferior product. Why? Because the more natural (raw) a honey is the more likely it is to crystallized or be sold in that form.
I purchase raw honey from a local beekeeper (sold at our natural food store) and my recent purchase looks like this:
I had two jars from the same MN beekeeper and one was liquid for about 1-2 weeks and the other solid (like you see above). How is that possible? Well, how fast a honey crystalizes depends on where the bees found their nectar. Example: nectar that comes from goldenrod is more likely to crystallized faster than nectar that comes from blackberries. So, the amount of sugar vs. water content is what contributes to the rate of crystallization or granulation.
Another factor affecting crystallization of honey is in how it's processed. Heating and filtering is what keeps it from crystalizing and both can destroy the healing benefits of honey. Commercial beekeepers will heat (pasteurize) up to 150 degrees F, filtering out all pollen, wax and other bee particles. Makes honey pretty but not healthy.
It's easy to make honey liquid again without destroying the beneficial components (nutrients and enzymes), all you have to do is warm it up a little. I prefer avoiding the microwave to do this, instead I'll use a pot of hot water (don't heat above 95 F) and set the honey jar inside til it is liquid again.
There is a huge misconception that pasteurizing (heating) makes the honey safer to consume. That is not why commercial beekeepers or companies do this, they do it because the customer prefers it. Not sure how that came to be but I'm assuming it is similar to why we preferred white soap over non-white...ADVERTISING! They market liquid & clear honey as "more appealing" to look at but in addition they'll also claim that their honey is also beneficial to your health when it isn't. What made it clear and liquid also destroyed its beneficial properties.
So, buy RAW and don't be afraid if it is crystallized or granulated or if it was once liquid and becomes crystallized or granulated. Honey does not expire in the way other foods do which is why you likely will not find an expiration date on locally made RAW honey from a small beekeeper. When commercial honey is sold it often has an expiration date on the bottle or a "best if used by" date. When you see this, remember it has nothing to do with the honey but more to do with the company selling it wanting you to buy another bottle. That expiration date in conjunction with the crystallization will make you think your honey has gone bad but that commercial honey was crap to begin with. It will still taste great and work fine in your tea, baking, etc… but it will not help you recover from a cold or sooth that sore throat the way RAW honey does. Much of the commercial honey now is being adulterated with ingredients such as high fructose corn syrup so its best to avoid anyway but now I'm drifting off topic.
End of point… crystallized honey is NOT bad :-)