If you want to know about Islam from an insider’s perspective, Seeking Allah, Finding Jesus by Nabeel Qureshi is simply a phenomenal book! Check out my book review by clicking here. Below are just a few of the quotes I found quite educational.
“There is much division in Islam. The best determination of whether a man is Muslim is if he exclusively declares that Allah is God and Mohammad is Allah’s messenger. Beyond this point, there is great diversity in Islam.”
“There is no book of sharia. We must derive the law from a hierarchy of sources using a process of jurisprudence called fiqh. The first and greatest source is the Quran. Nothing can supersede the Quran because it is the word of Allah. But the Koran is not comprehensive. As Muslims, there is much we must do and believe that is not found in the Quran. For this, we go to the second source, hadith. The hadith elaborate and clarify what is found in the Quran, but they never contradict. There is no contradiction in Islam. If a hadith is found in any way to contradict the Quran, then it is inauthentic and must be disregarded. If no hadith can be found to clarify an issue, then we must turn to the third source of sharia: the ulema, Muslim scholars who are wise and experienced in Islam.”
“Muftis from different schools of thought have different precedents and therefore provide different fatwas. Each denomination differs on what hadith they consider accurate. Since the hadith are the second rung of sharia, these differences of opinion have real consequences. Many of the differences between the ways Sunnis and Shias practice Islam are over this very matter. Their books of hadith are disparate. This difference, combined with the Shia position regarding the authority of imams, results in a significantly different view of sharia. … Most Muslims do not know these things. They know Islam to the extent that they practice it, and these are matters for the learned.”
“Christians believe Jesus is God incarnate, and this is a necessary belief for orthodox Christianity. Muslims believe that Jesus is no more than a prophet, and to consider Him God incarnate would be blasphemy and would cause one to be condemned to hell eternally, according to the Quran.”
“Regarding Jesus, there are two issues on which Muslims particularly disagree with Christians: that Jesus died on the Cross and that Jesus claimed to be God. The Quran specifically denies both of these beliefs.”
“Sahih Bukhari…is the most trustworthy book of hadith, compiled by Imam Bukhari. The hadith were not collected into the books until a long time after Mohammad’s death. Many false hadith had been fabricated, and it was difficult to determine which ones were accurate. Imam Bukhari sifted through five hundred thousand hadith and pick out the five thousand most accurate.”
“The earliest historical records show that Mohammad launched offensive military campaigns and used violence at times to accomplish his purposes. He used the term jihad in both spiritual and physical contexts, but the physical jihad is the one Mohammad strongly emphasizes. The peaceful practice of Islam hinges on later, often Western, interpretations of Mohammad’s teachings, whereas the more violent variations of Islam are deeply rooted in orthodoxy and history.”
“The Bible and the Quran were nothing alike. Not in the slightest. … Mohammad dictated the contents of the Quran to his scribes over a period of twenty-three years. Only after his death was the Quran collected into a book. Verses that had been dictated years or decades apart are frequently found side-by-side in the Quran, often with no obvious connection. The result is that Muslims placed relatively little weight on surrounding passages when trying to interpret sections of the Quran.”
“Almost everything Muslims know about Mohammad comes to them orally, rarely from primary sources. Unlike Christians learning about Jesus from the Bible, the Quran has very little to say about Mohammad.”
“Mohammad’s first biography, Sirat Rasul Allah by Ibn Ishaq, comes down to our date only through the transmission of a later biographer, Ibn Hisham. In his introduction, Ibn Hisham explains that he altered the story of Mohammad’s life. ‘Things which it is disgraceful to discuss, matters which would distressed certain people, and such reports as [my teacher] (sic) told me he could not accept as trustworthy—all these things I have omitted.’”
“According to the hadith, Mohammad named four men as the best teachers of the Quran. The first one was Abdullah ibn Mas’ud, whome Mohammad distinguished as the foremost expert of the Quran. The last one was Ubay ibn Ka’b, whom Sahih Bukhari identifies as the best reciter of the Quran. These were the men that Mohammad hand selected as the best teachers of the Quran, but as I studied the early sources, I found that they did not agree with the final Quran, which has been passed down as today’s version. They did not even agree with each other. … Ubay is known to have had 116 chapters in his Quran, two more than Zaid’s edition. Ibn Mas’ud had only 111 chapters in his Quran, insisting that the additional chapters in Zaid’s Quran and Ubay’s Quran were just prayers, not Quranic recitation.”
“In Islam, there is only one unforgivable sin, shirk, the belief that someone other than Allah is God. Shirk is specifically discussed in the context of Jesus in 5:72. He who believes Jesus is God, ‘Allah has forbidden Heaven for him, and his abode will be the Hellfire.’”
“All suffering is worth it to follow Jesus. He is amazing.”
“If you want a population to adopt your innovation, you have to create a problem that is solved by adoption. And that problem is almost always related to, ’what about the others?’” Check out this insight from Seth Godin on 
Craig T. Owens 