So If you would learn already about the market and the clients, what to buy,how increase its worth and where to sell it there is next thing:

• law (you must do things lawfuly,and law prohibits you from certain activities both in normal investing and on stock market
• proper time to sell (getting your profit maximal) and buy things
• where/what not to buy/not to sell

And if you think thing above,and previous post is too easy,too complex or too stupid - it is not.

Success on Gamestop required:

• Recognising market (how those stock automated systems work)
• Recognising opportunity
• Recognising client to profit (automated systems)
• Recognising how to invest and where (organising "monkeys" action about proper company)
• Recognising that law would allow that (of course funds are furious and behaved unlawfuly with the support of the government,but it was lawful at the time of doing it)

It is not one book or two.It is understanding how it (economy or only stock market - still requiring basic economy knowledge) all works,recognising opportunity,way to use this opportunity,its legality and taking risk to act. Or following advise what is risky unless you have trusty person.