It is not uncommon to suffer the "baby blues" following the birth of your baby. During the first one to two weeks you may find yourself tearful, having mood swings, being irritable (that's me!), and having a hard time sleeping. This is due to the sudden change in hormone levels, or an anti-climactic feeling after the birth of the baby.
Unlike these "blues" post-partum depression is longer-lasting and more serious, affecting 10-15% of women. You may experience deep feelings of hopelessness and despair, feel panicky, lethargic, etc. Should you notice these early warning signals it is critical to seek medical attention. Early treatment can be key! Don't suffer when there is help for you.
Here are some books:
Down Came the Rain: My Journey through Postpartum Depression by Brooke Shields
Mothering the New Mother: Your Postpartum Resource Companion by Sally Placksin
postpartum Survival Guide by Anne Dunnewold, Ph.D and Diane G. Sandford, Ph.D