True, but it also incorporated elements of the local pagan religion, to try and recruit them as well. Allah was considered first among many in the local pagan pantheon (which is why muhammad's uncle had been named after him, before muhammad was born). That is why you will sometimes hear freepers call Allah the Moon God - that was his role for the pagans, before his promotion by muhammad.
The Kaaba, the holiest site in islam which is the focus of the hajj pilgramage, was the main pagan shrine for pilgrimage, which was the biggest business in town before islam.
Salman Rushdie's "Satanic Verses" refers to the time that muhammad revealed as scripture from God, that more of the most popular pagan godesses (AllÄt, Uzza, and ManÄt) were recognized divine beings, able to intercede with Allah on behalf of supplicants, which a group of potential pagan recruits had been lobbying for. When his long term followers, who had taken lots of heat over the strict monotheism policy threatened to bolt, muhammad reversed himself, saying that the devil had forced him to say those things - hence the term Satanic Verses.
Kosher dietary restrictions became the almost identical Halal requirements (except that you have to say "Allah" when cutting the animals throat). The Christian Lenten Fast became Ramadan Fast. The Christian Liturgy of the Hours became the five requried daily prayers.
The great bulk of islam was cherry picked from the three competing religions, according to whatever would satisfy recruits to swear their oaths to him, and join his command for raiding parties (which grew into armies of conquest).
What is new and unique in islam is uniformly immoral or amoral, and geared totally toward politically supporting muhammad's absolute dictatorship and military conquests. The first and most important pillar of islam (Shahada) is original to islam - it is the oath affirming muhammad's absolute and unquestionable authority as the sole spokesperson for the only god. After accepting that outlandish premise, there can be no logic or reason - only obediance - submission. That is why they enforce it so heavily with the death penalty.