Hi, I have listed my two fav. books that I really enjoyed. Here they are:
Homebirth - Shelia Kitzinger - don't let the name turn you off, even if you are not planning on a homebirth this is a great resource and connects you to how beautiful birth can be - no matter where you decide to birth.
Birthing Normally - Gayle Peterson - This is a great resource on how your body knows what to do. Even if you do not connect with everything she says or recommends, I took what I needed from here and found it helpful.
Many friends liked the Shelia Kitzinger series, she has many books.
Suzanne Arms - Immaculate Deception is popular amoung natural birthing women
I highly recommend visiting the site for Birth Connection. They have well researched information.
Ina May is another great resource, I would agree with your friend Jen