Wittgenstein's masterpiece, published posthumously, is one of the most influential works of 20th century philosophy. Unlike most such books, this work is completely accessible to the non-specialist reader. He presents his ideas step by step, in a clearly argued way, in plain English (translated from the original German) and does not assume the usual prior knowledge of philosophers and philosophical arguments.
Wittgenstein starts from the thesis that, as philosophical discussion is based on language, we should first understand what language is and how it is used. Rather than assuming that words represent some deep buried meaning, he starts from a very simple pseudo-language and argues that "the meaning of a word is its use in the language."
Forget about the turgid commentaries on Wittgenstein's work and read the great man's actual words for yourself. They are self-explanatory. However, to appreciate his ideas properly, you will need to spend some time thinking about each section after you read it.