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I've not done either of those topics but I am doing History A level. For pre-WW2 Germany, I'd recommend Richard J Evan's book - I think it's called the Coming of the Third Reich - and more generally The Deluge by Adam Tooze is good too - it's not specifically on Germany but it's a global history between 1916 and 1931 so it covers it a bit! I don't know anything for the Ireland part of the course. Sorry!
I'm doing Ireland atm, the book we use is by Dr Rees, so I suppose if you are super keen you could read it in advance but I don't think it is really necessary there is also a book by Lyons 'Ireland since the famine' which my history teacher often makes reference to but again, it is a super dense book.