Books on how to be a good premed (if they exist) won't help you any better than a book on how to be a good college student. The general advice of studying very hard yet being well rounded by having extracurricular activities that you are passionate about along with doctor shadowing along with a little bit of research are what you need to do get an acceptance. As for what its like to be a premed...for me initially I just couldn't believe how much information that were expecting me to learn in my freshman bio class. Now that I'm done with med school, I feel like that course load from college was childs play compared to what they gave me in medical school. So don't feel bad if you feel overwhelmed initially, you will quickly adapt and excel just like you did in high school.