If you think HFT is quite hard and challenging, then Forex isn't any easier: you can still lose a ton of money over an unforseen event somewhere in the World.
More seriously, as someone who trades for a living, here's what I've learned (the hard way, i.e., losing my own money makes for expensive lessons):
Forex is one of the most volatile markets on this side of the "Milky Way". Only Commodities (Natural Gas for instance) beat it. The average range of noise (noise, random movement, not signal) is enough to loose huge amounts of money.
Forex brokers offer a stupid amount of leverage. 50x, 100x (and even 200x) leverage is not trading. It's gambling. Which means that if you want to stay in the game you need a lot of trading capital (want to make a million trading forex? Start with a billion).
Depends on your experience but, if you don't have a lot, start with stocks (CFDs, for instance) or indexes for deep markets.
If you still want to go the "Forex route", some reading material has to include:
Macroeconomics and Monetary Policy. You don't need a PhD on it, but you do need to grasp the basics of interest rates, currency parities, inflation, growth, central banking, capital movements.
Statistics. Again, no need for a PhD, but the basics are useful/helpful.
Money Management. People want the "holly grail strategy indicator" that gets you 9 out of 10 profitable trades. That's a myth. The best traders in the industry usually lose 2 out of every 3 trades. The point here is: you make up what you lose with the winning trade. So the real point is not how to enter (though it's still important) but to know when to "exit" the trade.
Basic trading strategies. Some apply better to Forex, other to Stocks, but in general the same principles apply.
And do take care: the Forex market is full of "Win x times your inicial amount in n days with our y fullproof strategy/platform" scammy proposition.