I read that a few years ago. It's not difficult at all; rather basic, in fact. If you want to understand how Islamic history feeds into the current politics of the Middle East, you're better off with something like Albert Hourani's "A History of the Arab Peoples", or John Darwin's "After Tamerlane: The Global History of Empire" for a more broad sweep. Lewis is a bit neocon and simplistic in his analysis. There's better stuff out there.
Myself, i'm nearing the end of Robert Fagles' translation of The Odyssey, which is impressive. I'm only reading it in preparation for Ulysses, which is going to be tough. To anyone thinking of tackling it - i've been told it pays to read Dubliners, A Portrait of the Artist as a Young Man and The Odyssey as kind of preparation.