As someone who had this in the breakfast cereal rotation as a kid I can confirm the textural differences between it and almost every other cereal. It is hard, crunchy, slightly sweet though definitely not near the level of other breakfast cereals, and has a unique flavor like wheat kernels.

It was fashionable decades ago as a healthy cereal and promoted by the famous Euell Gibbons, who would eat just about anything from nature. He is the reason that I have never shied away from sampling wild berries or leaves once I understand which plants grow in my area. There really are a lot of edible things that are overlooked since processed food is so easily obtained here in the US.

The experience of eating Grape Nuts can really be elevated by adding fresh or dried fruit and nuts like roasted pecans, roasted almonds, roasted walnuts, or similar nuts or you could substitute candied nuts coated with honey, cinnamon sugar, praline, etc.

Personally, if I ever eat Grape Nuts again they will be used as a topping on ice cream combined with dark chocolate syrup or fudge, some nuts, and a little dried fruit. This gives the ice cream an awesome texture boost and the melding of the flavors is fantastic.

I currently use home-made granola base as a breakfast and spruce it up with various things every morning so the flavor experience doesn't get old. My wife makes excellent granola and it is super simple. Oats are one of my favorite grains.