Bitter rue or herb of grace was known in the ancient world. The major use of this herb of grace was an antidote for all kinds of poisons.
Romans cultivated rue herb - they called it Mars' herb, because it was used as a purifying agent for cleaning Iron (the metal of mars) - they grew this herb around temples of Mars. It was also considered to be the Mars' herb, because it can be fierce as god Mars. Its essential oil can be a very irritating agent and can easily cause burns and blisters on skin if applied.
Herb of grace was also widely used in the Middle Ages. Rue was hung under the door as a protection from evil spirits. People used to throw the bunch of rue in their enemy cursing him (that is where the expression "rue the day" has come from). In some European countries special amulets were made out of rue herb.
But why rue is called herb of grace? This interesting name for that herb came in use, because in old times priests were splashing holy water with the bunch of rue herb during Mass. Herb of grace was also used during exorcisms. Rue as a herb of grace is even mentioned in works of Shakespeare. Some people also believed that rue herb can stimulate clairvoyance and open the third eye.
The medical use of rue is very wide. It can be used to stimulate the work of digestive system or as antiseptic. Hippocrates used it as diuretic mean and a fever remedy. For a long time it was also known as an agent that affects the female reproductive tract, so it was used to initiate menstrual periods, as contraceptive agent, and to cause the abortion.
As a kitchen herb leaves of the rue herb are mostly used. Because of their bitter taste, rue leaves stimulate appetite and can be added into different salads and sauces. The very strong aroma of rue herb can significantly improve the taste of meat and fish dishes. Herb of grace match very well with many other herbs and spices, which make it possible to use it in different herb mixtures to achieve better taste of your dishes.
If you don't like bitter taste of this herb pretty much, then you can add something that contains acid (rue herb is often added into vinegar). As long as rue gives away its flavor faster then bitterness you can get it aroma without bitter taste by putting bunch of rue in boiling water(sauce) for minute or so and take it away after that. If you put rue herb into oil (that is intended for cooking or making salads) then you will also get less bitter taste. And as far as the taste and aroma of rue herb are very strong you need only small quantity for cooking.
No matter what quantities of rue herb you are using you still have to be careful with this plant. There are not many rue recipes available, because many people consider cooking with rue to be an old-fashioned manner, but you should definitely try this herb in your dishes at least once.
Try Internet search, for there are many web sites dedicated to the herb, which can provide you with needed recipes. These days rue herb is used not only for cookery, but also as a garden plant. It can be easily cultivated in any garden in place with enough sun and watering.