Leadership entails a person who can be above traditional bias and make clear, informed decisions that can direct a group placed in his care. The decision should be for the collective good, and not have any selfish motivations of any kind.
You will act on behalf of the group at all times, and make decisions based on judgement that is driven only by honesty and transparency. In some ways, you need to ensure that everyone is happy with your decisions involving the group. You can't always please everyone, and you're not perfect, but it is your duty to do what you feel is correct, stick to the rules(ethics, adhere to a general code of conduct) as much as possible and act honorably and conscientiously.
It is important for a leader to also be humble and welcome feedback. He must have regular meetings and listen to what each person in the group has to say, and not shoot down any input, but be able to patiently draw it out, put it on the table for discussion, encourage further research by each person in the group so that they will be able to discuss each idea completely and correctly before deciding on which ideas all of you agree on. He also must keep himself updated, find out as much as possible about the information on the subject/topic the group is working on. That helps him to make balanced decisions.
It would be even better if the leader can encourage each person to do a lot of research on the idea they are about to put forth before a meeting, and to put the copious information in an understandable order, stating the pros and cons clearly, and giving all relevant information to help others make decisions as well. This is because each person can't read everything. You can divide the work carefully and expect each person to do as much research as possible in that part of the assignment, and then share its highlights with the rest of the group, though.
This way, you cover more ground and involve everyone in the group work, while making each person feel like an important constituent of the group. You must also trust that each person is giving their best and only encourage, and not enforce anything. You can suggest, and in the worst case scenario, you can insist, but you may not enforce or punish because respect and trust works both ways.
Most importantly, a leader must be wise, patient, friendly and approachable, while being firm - ONLY where necessary. It is important to understand that they are not better individuals - mere coordinators, and that their principal purpose is to coordinate things.
Under a good leader, everybody wins in the end, even if it seems like a mess in the beginning.
Honestly, I haven't quite come across a book that holds all the information necessary to be a good leader.