Well, I wouldn't necessarily say that he was interested in Islam. In respect to a proclaimation about the Mamluks, Andrew Roberts states that "Napoleon was not afraid to invoke the deity - even to appear to take the side of the Muslims against the Pope - if it would serve his purpose and win over the population." (Roberts, Napoleon: A Life, 169).

Even a few pages later (174) Napoleon thinks to embrace Islam but to never go so far as "that fool Menou" "who married an Egyptian, converted to Islam and took on the middle name Abdullah." However, the most important thing is what Roberts later says, "Asked two decades later whether he had ever truly embraced Islam, Napoleon laugingly replied: 'Fighting is a soldier's religion; I never changed that. The other is the affair of women and priests. As for me, I always adopt the religion of the country I am in." (ibid)

His interest with Islam came from a political will more so than a personal will. It is true that on travelling to Egypt for his campaign he read and familiarised himself with the Koran but this is likely just so as to impress local dignitaries during negotiations and his otherwise secular, border line atheist writings throughout his life mention nothing of the Koran as far as I'm aware.

Source: Napoleon The Great, Andrew Roberts Napoleon, Alan Forrest