I read Darwin's Origin of Species and it made perfect sense to me. It is not just a brief pamphlet outlining an idea of evolution. It is a 500-page compendium of evidence for it.

As for ID... there is no such thing as "irreducible complexity", the term itself is an invention of author Michael Behe which he used in his 1996 book "Darwin's Black Box", arguing in favor of intelligent design. The term is found nowhere else.

The two books are not to be put in the same class. The are simply not at the same formal academic level. You can easily see this by comparing the contents of the two:

1. Table of Contents, Origin of Species (author Charles Darwin)

2. Table of Contents, Darwins Black Box (author Michael Behe)

The exquisite detail and thoroughness of Charles Darwin's book which positively drips with hands-on experience - which demonstrates a lifetime of work in the field - is what makes it one of the most respected works of science ever written. Simply put, it is unsurpassed. And you won't find a univeristy-level biology textbook in use that does not begin with, and further expand on, his work.