The Koran is not arranged in chronological order, Atalanta. The revelations occurred over a period of twenty odd years, and usually a have relevance to particular events in the life of the Prophet. The chronologically earlier suras were revealed at Mecca when Mohammed was trying to persuade his fellow Meccans to abandon polytheism and accept him as the messenger of the one true God. That's where you find the references to his critics who said that the revelations were Mohammed's own invention. (No man could invent something as sublime as this book is the Koran's response). Then Mohammed migrates to Medina where his efforts at proselytising are far more successful, and he begins a campaign of attacking the camel trains which sustained Meccan commerce. So you get further revelations which deal with his arguments with the Medinan Jews, the division of the spoils (Sura 8 is called "Booty" in my translation) and exhortations and comments on the battles which ensued between the Muslims and the Meccans. Then later still we get the revelations after Mohammed's successful return to and conquest of Mecca. These (such as Sura 9) stress the duty of Muslims to fight in the cause of Allah until the goal of universal submission to the divine will is achieved.
In the absence of this context the book is largely unintelligible, as you correctly observe.
I've read the Koran in the following form. It's author is clearly hostile to Islam and appears (at least to me) to be a rather charmless man, but he has arranged the Koran in chronological order and intersperses selected passages with the important biographical details:
http://www.politicalislam.com/product/an-abridged-koran/
Your assessment reflects that of Thomas Carlyle over 150 years ago:
"I must say, it is as toilsome reading as I ever undertook. A wearisome confused jumble, crude, incondite; endless iterations, long-windedness, entanglement; most crude, incondite; -- insupportable stupidity, in short! Nothing but a sense of duty could carry any European through the Koran.".
Carlyle would approve your sense of duty.