Part of first aid education I think is instruction on when not to do what's in books Crowe - to do no harm. Simple wounds are just that, basic first aid will treat them, and really simple wounds require no real assistance - apply pressure, keep things clean everything should turn out ok. More complex medical assistance requires certified training, and without some basic training you won't really know when you have gone over the edge into a more complex, potentially life-threatening scenario. The decision to give first aid to another human being is a serious one, applying all your training and experience and fraught with general and specific personal liability for your actions. Without some instruction, you'll be reading the book when you should be applying pressure, or giving aid. Without a certified course in first aid, your response to anyone that asks if you have any first aid experience (employers, volunteer organizations, CERTs, friends, a patient lying on the ground with a compound fracture, etc), is "no." Anyone for whom it really matters does not want to be treated by the guy who slept the previous night in a Holiday Inn, so he must miraculously be transformed into a neurosurgeon. Once you have taken a course, you can say "Yes, I'm trained in [Wilderness First Aid], can I help you," and generally get right to work.

A course that gives you hands on experience in treating wounds, immobilizing fractures, assessing and evacuating patients has been best in my experience. For general preparedness, save up $175-200, and take a Wilderness First Aid course from NOLS / (Wilderness Medical Institute) or the American Red Cross. The 2 day course is legit, and gives you some very valuable first aid skills that you will apply in life or in your planned preparedness activities. The certified training expires every 2 years, so if you want to keep it up you should similarly save up and re-take the course, like medicine the curriculum changes often enough to justify the cost. Plus they give you a decent, small medical reference that covers what you learn.

Once you have certified training, you will have a better sense of what first aid book references will be useful to you.

Also I think it is the price of admission to a civilized society and marks you as a civilized man/woman, that you take a CPR / AED course - not all courses are free, but generally speaking you can qualify for a free one though school, or an employer, or by volunteering with certain agencies (although even the Red Cross doesn't provide free CPR training anymore except for its actual employees). And check with your local emergency management agency or fire district, they often hold CPR fairs or other ways to learn and be certified (there's that word again) in CPR.

Last, practice - find out who provides the first aid station at local 5K and half marathons, and see if you can sign up to assist. That may get you into their required first aid training, and it will give you some hands on experience in doing real life first aid. Learning from those with more experience is always good, and frankly I've lived my whole life by that rule. If you look hard enough you may find other volunteer opportunities to learn and apply your first aid skills.

Book learned first aid folks might be relied on to hold a bandage on a wound, but not to assist with providing actual first aid. Get trained, you'll be more prepared to help real people.