Reviews

Although certainly dated, "Aspects" is an admirable and, to date, unsurpassed attempt at defining a theory for the study of language, with coherent, consistent and systematic scientific grounding.
Many points made in the book will seem to the modern reader very clearly misguided and at times circular, but since it's publication it's been the analytical basis for the study of language and bears influence further still in the foundations of cognitive psychology, which last to this day.
Personally, I find this book to be the place to go if you wanna learn the formal approach to linguistics, however, to learn the subject seriously and adequately, there'll be some decades of research to update yourself with.
If you are new to Linguistics: this is where to start.
If you're interested in cognitive psych: right this way
If you're interested in philosophy: take a good look here
Landmark book, but you need to take it for what it is. A place to learn where to move from.  

A great leap forward on the long way down.