First off, forget about systems. Just say to yourself, if this system worked, why is he trying to sell it to me. Books are worth reading as long as they are used as an enrichment to your betting, not a cause.
Unfortunately, like most things in life, getting told something doesnt sink in, its only when you experience it yourself that you take notice. Learning from your mistakes will always be the best teacher, thats why all the smart know-it-alls are old. Its through experience of seeing something over and over that makes you aware of the potential outcomes and pitfalls, an example is, posters talking about Nadal winning the French Open, at 1/6, who cares, certainly not someone who is seriously trying to make money gambling.
I find this Forum, like most, seem to give the impression that there is many Pros on here, from my own experience and others in the game, the truth is, you wouldnt have the time to play around on here, but it is fun. A pro gamblers World is a very insular, selfish one and looking back, a regretable one. Its not said enough on this Forum, but there is a big difference between making your gambling hobby pay ( like I do at the moment) and making a living out of it, people talk of 5% winning, its 1 in 10,000 earns a living.
If theres one big killer for the average punter, then its backing odds-on, this is where the reading books can become dangerous. Betting odds-on can be profitable, but only to the most knowledgeable ( odds wise) and well endowed bank punter, for the rest it is suicide.