Yes, I use them as my primary means of maintaining my health. I have used herbs medicinally that I would not generally recommend to others, such as bitersweet nightshade and mistletoe.
I would suggest building a library with a number of types of works. These might include serious works on naturopathy (like The Encyclopedia of Natural Medicine), good books on herbs (The Healing Herbs by Michael Castleman), and maybe a few others. I have a few rare herbals self-published by friends of mine with a great deal of experience.
A few things to look for:
1) A good book will provide cautions about each herb. Many herbs, such as comfrey are dangerous if taken improperly, i.e. if you are healthy drink 20 cups of comfrey tea a day, you may develop liver damage, but if you drink 2 cups of comfrey tea a day and already have liver damage, you are really asking for trouble.
2) Check the bibliography.